Package 'tidypolars'

Title: Get the Power of Polars with the Syntax of the Tidyverse
Description: Polars is an amazing cross-language tool for manipulating very large data. However, one drawback is that the R implementation has a syntax that will look odd to many R users who are not used to Python syntax. The objective of tidypolars is to improve the ease-of-use of Polars in R by providing tidyverse syntax to polars.
Authors: Etienne Bacher [aut, cre, cph]
Maintainer: Etienne Bacher <[email protected]>
License: MIT + file LICENSE
Version: 0.12.0
Built: 2024-11-19 16:27:37 UTC
Source: https://github.com/etiennebacher/tidypolars

Help Index

Order rows using column values

Description

Order rows using column values

Usage

## S3 method for class 'RPolarsDataFrame'
arrange(.data, ..., .by_group = FALSE)

Arguments

.data

A Polars Data/LazyFrame
...

Variables, or functions of variables. Use desc() to sort a variable in descending order.
.by_group

If TRUE, will sort data within groups.

Examples

pl_test <- polars::pl$DataFrame(
  x1 = c("a", "a", "b", "a", "c"),
  x2 = c(2, 1, 5, 3, 1),
  value = sample(1:5)
)

arrange(pl_test, x1)
arrange(pl_test, x1, -x2)

# if the data is grouped, you need to specify `.by_group = TRUE` to sort by
# the groups first
pl_test |>
  group_by(x1) |>
  arrange(-x2, .by_group = TRUE)

Convert a Polars DataFrame to an R data.frame or to a tibble

Description

This makes it easier to convert a polars DataFrame or LazyFrame to a tibble in a pipe workflow.

Usage

## S3 method for class 'tidypolars'
as_tibble(x, int64_conversion = polars::polars_options()$int64_conversion, ...)

Arguments

x

A Polars Data/LazyFrame
int64_conversion

How should Int64 values be handled when converting a polars object to R? See the documentation in polars::as.data.frame.RPolarsDataFrame.
...

Options passed to polars::as.data.frame.RPolarsDataFrame.

About int64

Int64 is a format accepted in Polars but not natively in R (the package bit64 helps with that).

Since tidypolars is simply a wrapper around polars, the behavior of int64 values will depend on the options set in polars. Use options(polars.int64_conversion =) to specify how int64 variables should be handled. See the documentation in polars for the possible options.

Examples

iris |>
  as_polars_df() |>
  filter(Sepal.Length > 6) |>
  as_tibble()

Append multiple Data/LazyFrames next to each other

Description

Append multiple Data/LazyFrames next to each other

Usage

bind_cols_polars(..., .name_repair = "unique")

Arguments

...

Polars DataFrames or LazyFrames to combine. Each argument can either be a Data/LazyFrame, or a list of Data/LazyFrames. Columns are matched by name. All Data/LazyFrames must have the same number of rows and there mustn't be duplicated column names.
.name_repair

Can be "unique", "universal", "check_unique", "minimal". See vctrs::vec_as_names() for the explanations for each value.

Examples

p1 <- polars::pl$DataFrame(
  x = sample(letters, 20),
  y = sample(1:100, 20)
)
p2 <- polars::pl$DataFrame(
  z = sample(letters, 20),
  w = sample(1:100, 20)
)

bind_cols_polars(p1, p2)
bind_cols_polars(list(p1, p2))

Stack multiple Data/LazyFrames on top of each other

Description

Stack multiple Data/LazyFrames on top of each other

Usage

bind_rows_polars(..., .id = NULL)

Arguments

...

Polars DataFrames or LazyFrames to combine. Each argument can either be a Data/LazyFrame, or a list of Data/LazyFrames. Columns are matched by name, and any missing columns will be filled with NA.
.id

The name of an optional identifier column. Provide a string to create an output column that identifies each input. If all elements in ... are named, the identifier will use their names. Otherwise, it will be a simple count.

Examples

library(polars)
p1 <- pl$DataFrame(
  x = c("a", "b"),
  y = 1:2
)
p2 <- pl$DataFrame(
  y = 3:4,
  z = c("c", "d")
)$with_columns(pl$col("y")$cast(pl$Int16))

bind_rows_polars(p1, p2)

# this is equivalent
bind_rows_polars(list(p1, p2))

# create an id colum
bind_rows_polars(p1, p2, .id = "id")

# create an id colum with named elements
bind_rows_polars(p1 = p1, p2 = p2, .id = "id")

Complete a data frame with missing combinations of data

Description

Turns implicit missing values into explicit missing values. This is useful for completing missing combinations of data.

Usage

## S3 method for class 'RPolarsDataFrame'
complete(data, ..., fill = list())

## S3 method for class 'RPolarsLazyFrame'
complete(data, ..., fill = list())

Arguments

data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
fill

A named list that for each variable supplies a single value to use instead of NA for missing combinations.

Examples

df <- polars::pl$DataFrame(
  group = c(1:2, 1, 2),
  item_id = c(1:2, 2, 3),
  item_name = c("a", "a", "b", "b"),
  value1 = c(1, NA, 3, 4),
  value2 = 4:7
)
df

df |> complete(group, item_id, item_name)

df |>
  complete(
    group, item_id, item_name,
    fill = list(value1 = 0, value2 = 99)
  )

df |>
  group_by(group, maintain_order = TRUE) |>
  complete(item_id, item_name)

Collect a LazyFrame

Description

compute() checks the query, optimizes it in the background, and runs it. The output is a Polars DataFrame. collect() is similar to compute() but converts the output to an R data.frame, which consumes more memory.

Until tidypolars 0.7.0, there was only collect() and it was used to collect a LazyFrame into a Polars DataFrame. This usage is still valid for now but will change in 0.8.0 to automatically convert a DataFrame to a data.frame. Use compute() to have a Polars DataFrame as output.

Usage

## S3 method for class 'RPolarsLazyFrame'
compute(
  x,
  ...,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  comm_subplan_elim = TRUE,
  comm_subexpr_elim = TRUE,
  cluster_with_columns = TRUE,
  no_optimization = FALSE,
  streaming = FALSE,
  collect_in_background = FALSE
)

## S3 method for class 'RPolarsLazyFrame'
collect(
  x,
  ...,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  comm_subplan_elim = TRUE,
  comm_subexpr_elim = TRUE,
  cluster_with_columns = TRUE,
  no_optimization = FALSE,
  streaming = FALSE,
  collect_in_background = FALSE
)

Arguments

x

A Polars LazyFrame
...

Not used.
type_coercion

Coerce types such that operations succeed and run on minimal required memory (default is TRUE).
predicate_pushdown

Applies filters as early as possible at scan level (default is TRUE).
projection_pushdown

Select only the columns that are needed at the scan level (default is TRUE).
simplify_expression

Various optimizations, such as constant folding and replacing expensive operations with faster alternatives (default is TRUE).
slice_pushdown

Only load the required slice from the scan. Don't materialize sliced outputs level. Don't materialize sliced outputs (default is TRUE).
comm_subplan_elim

Cache branching subplans that occur on self-joins or unions (default is TRUE).
comm_subexpr_elim

Cache common subexpressions (default is TRUE).
cluster_with_columns

Combine sequential independent calls to ⁠$with_columns()⁠.
no_optimization

Sets the following optimizations to FALSE: predicate_pushdown, projection_pushdown, slice_pushdown, simplify_expression. Default is FALSE.
streaming

Run parts of the query in a streaming fashion (this is in an alpha state). Default is FALSE.
collect_in_background

Detach this query from the R session. Computation will start in background. Get a handle which later can be converted into the resulting DataFrame. Useful in interactive mode to not lock R session (default is FALSE).

See Also

fetch() for applying a lazy query on a subset of the data.

Examples

dat_lazy <- polars::as_polars_df(iris)$lazy()

compute(dat_lazy)

# you can build a query and add compute() as the last piece
dat_lazy |>
  select(starts_with("Sepal")) |>
  filter(between(Sepal.Length, 5, 6)) |>
  compute()

# call collect() instead to return a data.frame (note that this is more
# expensive than compute())
dat_lazy |>
  select(starts_with("Sepal")) |>
  filter(between(Sepal.Length, 5, 6)) |>
  collect()

Count the observations in each group

Description

Count the observations in each group

Usage

## S3 method for class 'RPolarsDataFrame'
count(x, ..., sort = FALSE, name = "n")

## S3 method for class 'RPolarsLazyFrame'
count(x, ..., sort = FALSE, name = "n")

## S3 method for class 'RPolarsDataFrame'
add_count(x, ..., sort = FALSE, name = "n")

## S3 method for class 'RPolarsLazyFrame'
add_count(x, ..., sort = FALSE, name = "n")

Arguments

x

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
sort

If TRUE, will show the largest groups at the top.
name

Name of the new column.

Examples

test <- polars::as_polars_df(mtcars)
count(test, cyl)

count(test, cyl, am)

count(test, cyl, am, sort = TRUE, name = "count")

add_count(test, cyl, am, sort = TRUE, name = "count")

Cross join

Description

Cross joins match each row in x to every row in y, resulting in a dataset with nrow(x) * nrow(y) rows.

Usage

## S3 method for class 'RPolarsDataFrame'
cross_join(x, y, suffix = c(".x", ".y"), ...)

## S3 method for class 'RPolarsLazyFrame'
cross_join(x, y, suffix = c(".x", ".y"), ...)

Arguments

x, y

Two Polars Data/LazyFrames
suffix

If there are non-joined duplicate variables in x and y, these suffixes will be added to the output to disambiguate them. Should be a character vector of length 2.
...

Not used.

Examples

test <- polars::pl$DataFrame(
  origin = c("ALG", "FRA", "GER"),
  year = c(2020, 2020, 2021)
)

test2 <- polars::pl$DataFrame(
  destination = c("USA", "JPN", "BRA"),
  language = c("english", "japanese", "portuguese")
)

test

test2

cross_join(test, test2)

Summary statistics for a Polars DataFrame

Description

[Deprecated]

This function is deprecated as of tidypolars 0.10.0, it will be removed in a future update. Use summary() with the same arguments instead.

Usage

describe(.data, percentiles = c(0.25, 0.75))

Arguments

.data

A Polars DataFrame.
percentiles

One or more percentiles to include in the summary statistics. All values must be between 0 and 1 (NULL are ignored).

Show the optimized and non-optimized query plans

Description

[Deprecated]

Those functions are deprecated as of tidypolars 0.10.0, they will be removed in a future update. Use explain() with optimized = FALSE to recover the output of describe_plan(), and with optimized = TRUE (the default) to get the output of describe_optimized_plan().

Usage

describe_plan(.data)

describe_optimized_plan(.data)

Arguments

.data

A Polars LazyFrame

Remove or keep only duplicated rows in a Data/LazyFrame

Description

By default, duplicates are looked for in all variables. It is possible to specify a subset of variables where duplicates should be looked for. It is also possible to keep either the first occurrence, the last occurence or remove all duplicates.

Usage

## S3 method for class 'RPolarsDataFrame'
distinct(.data, ..., keep = "first", maintain_order = TRUE)

## S3 method for class 'RPolarsLazyFrame'
distinct(.data, ..., keep = "first", maintain_order = TRUE)

duplicated_rows(.data, ...)

Arguments

.data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
keep

Either "first" (keep the first occurrence of the duplicated row), "last" (last occurrence) or "none" (remove all ofccurences of duplicated rows).
maintain_order

Maintain row order. This is the default but it can slow down the process with large datasets and it prevents the use of streaming.

Examples

pl_test <- polars::pl$DataFrame(
  iso_o = c(rep(c("AA", "AB"), each = 2), "AC", "DC"),
  iso_d = rep(c("BA", "BB", "BC"), each = 2),
  value = c(2, 2, 3, 4, 5, 6)
)

distinct(pl_test)
distinct(pl_test, iso_o)

duplicated_rows(pl_test)
duplicated_rows(pl_test, iso_o, iso_d)

Drop missing values

Description

By default, this will drop rows that contain any missing values. It is possible to specify a subset of variables so that only missing values in these variables will be considered.

Usage

## S3 method for class 'RPolarsDataFrame'
drop_na(data, ...)

## S3 method for class 'RPolarsLazyFrame'
drop_na(data, ...)

Arguments

data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.

Examples

tmp <- mtcars
tmp[1:3, "mpg"] <- NA
tmp[4, "hp"] <- NA
pl_tmp <- polars::pl$DataFrame(tmp)

drop_na(pl_tmp)
drop_na(pl_tmp, hp, mpg)

Show the optimized and non-optimized query plans

Description

This function is available for LazyFrames only.

By default, explain() shows the query plan that is optimized and then run by Polars. Setting optimized = FALSE shows the query plan as-is, without any optimization done, but this not the query performed. Note that the plans are read from bottom to top.

Usage

## S3 method for class 'RPolarsLazyFrame'
explain(x, optimized = TRUE, ...)

Arguments

x

A Polars LazyFrame.
optimized

Logical. If TRUE (default), show the query optimized by Polars. Otherwise, show the initial query.
...

Ignored.

Examples

query <- mtcars |>
  as_polars_lf() |>
  arrange(drat) |>
  filter(cyl == 3) |>
  select(mpg)

# unoptimized query plan:
no_opt <- explain(query, optimized = FALSE)
no_opt

# better printing with cat():
cat(no_opt)

# optimized query run by polars
cat(explain(query))

Fetch n rows of a LazyFrame

Description

Fetch is a way to collect only the first n rows of a LazyFrame. It is mainly used to test that a query runs as expected on a subset of the data before using collect() on the full query. Note that fetching n rows doesn't mean that the output will actually contain n rows, see the section 'Details' for more information.

Usage

fetch(
  .data,
  n_rows = 500,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  comm_subplan_elim = TRUE,
  comm_subexpr_elim = TRUE,
  cluster_with_columns = TRUE,
  no_optimization = FALSE,
  streaming = FALSE
)

Arguments

.data

A Polars LazyFrame
n_rows

Number of rows to fetch.
type_coercion

Coerce types such that operations succeed and run on minimal required memory (default is TRUE).
predicate_pushdown

Applies filters as early as possible at scan level (default is TRUE).
projection_pushdown

Select only the columns that are needed at the scan level (default is TRUE).
simplify_expression

Various optimizations, such as constant folding and replacing expensive operations with faster alternatives (default is TRUE).
slice_pushdown

Only load the required slice from the scan. Don't materialize sliced outputs level. Don't materialize sliced outputs (default is TRUE).
comm_subplan_elim

Cache branching subplans that occur on self-joins or unions (default is TRUE).
comm_subexpr_elim

Cache common subexpressions (default is TRUE).
cluster_with_columns

Combine sequential independent calls to ⁠$with_columns()⁠.
no_optimization

Sets the following optimizations to FALSE: predicate_pushdown, projection_pushdown, slice_pushdown, simplify_expression. Default is FALSE.
streaming

Run parts of the query in a streaming fashion (this is in an alpha state). Default is FALSE.

Details

The parameter n_rows indicates how many rows from the LazyFrame should be used at the beginning of the query, but it doesn't guarantee that n_rows will be returned. For example, if the query contains a filter or join operations with other datasets, then the final number of rows can be lower than n_rows. On the other hand, appending some rows during the query can lead to an output that has more rows than n_rows.

See Also

collect() for applying a lazy query on the full data.

Examples

dat_lazy <- polars::as_polars_df(iris)$lazy()

# this will return 30 rows
fetch(dat_lazy, 30)

# this will return less than 30 rows because there are less than 30 matches
# for this filter in the whole dataset
dat_lazy |>
  filter(Sepal.Length > 7.0) |>
  fetch(30)

Fill in missing values with previous or next value

Description

Fills missing values in selected columns using the next or previous entry. This is useful in the common output format where values are not repeated, and are only recorded when they change.

Usage

## S3 method for class 'RPolarsDataFrame'
fill(data, ..., .direction = c("down", "up", "downup", "updown"))

Arguments

data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
.direction

Direction in which to fill missing values. Either "down" (the default), "up", "downup" (i.e. first down and then up) or "updown" (first up and then down).

Details

With grouped Data/LazyFrames, fill() will be applied within each group, meaning that it won't fill across group boundaries.

Examples

pl_test <- polars::pl$DataFrame(x = c(NA, 1), y = c(2, NA))

fill(pl_test, everything(), .direction = "down")
fill(pl_test, everything(), .direction = "up")

# with grouped data, it doesn't use values from other groups
pl_grouped <- polars::pl$DataFrame(
  grp = rep(c("A", "B"), each = 3),
  x = c(1, NA, NA, NA, 2, NA),
  y = c(3, NA, 4, NA, 3, 1)
) |>
  group_by(grp)

fill(pl_grouped, x, y, .direction = "down")

Keep rows that match a condition

Description

This function is used to subset a data frame, retaining all rows that satisfy your conditions. To be retained, the row must produce a value of TRUE for all conditions. Note that when a condition evaluates to NA the row will be dropped, unlike base subsetting with [.

Usage

## S3 method for class 'RPolarsDataFrame'
filter(.data, ..., .by = NULL)

## S3 method for class 'RPolarsLazyFrame'
filter(.data, ..., .by = NULL)

Arguments

.data

A Polars Data/LazyFrame
...

Expressions that return a logical value, and are defined in terms of the variables in the data. If multiple expressions are included, they will be combined with the & operator. Only rows for which all conditions evaluate to TRUE are kept.
.by

Optionally, a selection of columns to group by for just this operation, functioning as an alternative to group_by(). The group order is not maintained, use group_by() if you want more control over it.

Examples

pl_iris <- polars::as_polars_df(iris)

filter(pl_iris, Sepal.Length < 5, Species == "setosa")

filter(pl_iris, Sepal.Length < Sepal.Width + Petal.Length)

filter(pl_iris, Species == "setosa" | is.na(Species))

iris2 <- iris
iris2$Species <- as.character(iris2$Species)
iris2 |>
  as_polars_df() |>
  filter(Species %in% c("setosa", "virginica"))

# filter by group
pl_iris |>
  group_by(Species) |>
  filter(Sepal.Length == max(Sepal.Length)) |>
  ungroup()

# an alternative syntax for grouping is to use `.by`
pl_iris |>
  filter(Sepal.Length == max(Sepal.Length), .by = Species)

Import data from CSV file(s)

Description

read_csv_polars() imports the data as a Polars DataFrame.

scan_csv_polars() imports the data as a Polars LazyFrame.

Usage

read_csv_polars(
  source,
  ...,
  has_header = TRUE,
  separator = ",",
  comment_prefix = NULL,
  quote_char = "\"",
  skip_rows = 0,
  dtypes = NULL,
  null_values = NULL,
  ignore_errors = FALSE,
  cache = FALSE,
  infer_schema_length = 100,
  n_rows = NULL,
  encoding = "utf8",
  low_memory = FALSE,
  rechunk = TRUE,
  skip_rows_after_header = 0,
  row_index_name = NULL,
  row_index_offset = 0,
  try_parse_dates = FALSE,
  eol_char = "\n",
  raise_if_empty = TRUE,
  truncate_ragged_lines = FALSE,
  reuse_downloaded = TRUE
)

scan_csv_polars(
  source,
  ...,
  has_header = TRUE,
  separator = ",",
  comment_prefix = NULL,
  quote_char = "\"",
  skip_rows = 0,
  dtypes = NULL,
  null_values = NULL,
  ignore_errors = FALSE,
  cache = FALSE,
  infer_schema_length = 100,
  n_rows = NULL,
  encoding = "utf8",
  low_memory = FALSE,
  rechunk = TRUE,
  skip_rows_after_header = 0,
  row_index_name = NULL,
  row_index_offset = 0,
  try_parse_dates = FALSE,
  eol_char = "\n",
  raise_if_empty = TRUE,
  truncate_ragged_lines = FALSE,
  reuse_downloaded = TRUE
)

Arguments

source

Path to a file or URL. It is possible to provide multiple paths provided that all CSV files have the same schema. It is not possible to provide several URLs.
...

Ignored.
has_header

Indicate if the first row of dataset is a header or not.If FALSE, column names will be autogenerated in the following format: "column_x" x being an enumeration over every column in the dataset starting at 1.
separator

Single byte character to use as separator in the file.
comment_prefix

A string, which can be up to 5 symbols in length, used to indicate the start of a comment line. For instance, it can be set to ⁠#⁠ or ⁠//⁠.
quote_char

Single byte character used for quoting. Set to NULL to turn off special handling and escaping of quotes.
skip_rows

Start reading after a particular number of rows. The header will be parsed at this offset.
dtypes

Named list of column names - dtypes or dtype - column names. This list is used while reading to overwrite dtypes. Supported types so far are:

  • "Boolean" or "logical" for DataType::Boolean,

  • "Categorical" or "factor" for DataType::Categorical,

  • "Float32" or "double" for DataType::Float32,

  • "Float64" or "float64" for DataType::Float64,

  • "Int32" or "integer" for DataType::Int32,

  • "Int64" or "integer64" for DataType::Int64,

  • "String" or "character" for DataType::String,

null_values

Values to interpret as NA values. Can be:

  • a character vector: all values that match one of the values in this vector will be NA;

  • a named list with column names and null values.

ignore_errors

Keep reading the file even if some lines yield errors. You can also use infer_schema_length = 0 to read all columns as UTF8 to check which values might cause an issue.
cache

Cache the result after reading.
infer_schema_length

Maximum number of rows to read to infer the column types. If set to 0, all columns will be read as UTF-8. If NULL, a full table scan will be done (slow).
n_rows

Maximum number of rows to read.
encoding

Either "utf8" or "utf8-lossy". Lossy means that invalid UTF8 values are replaced with "?" characters.
low_memory

Reduce memory usage (will yield a lower performance).
rechunk

Reallocate to contiguous memory when all chunks / files are parsed.
skip_rows_after_header

Parse the first row as headers, and then skip this number of rows.
row_index_name

If not NULL, this will insert a row index column with the given name into the DataFrame.
row_index_offset

Offset to start the row index column (only used if the name is set).
try_parse_dates

Try to automatically parse dates. Most ISO8601-like formats can be inferred, as well as a handful of others. If this does not succeed, the column remains of data type pl$String.
eol_char

Single byte end of line character (default: ⁠\n⁠). When encountering a file with Windows line endings (⁠\r\n⁠), one can go with the default ⁠\n⁠. The extra ⁠\r⁠ will be removed when processed.
raise_if_empty

If FALSE, parsing an empty file returns an empty DataFrame or LazyFrame.
truncate_ragged_lines

Truncate lines that are longer than the schema.
reuse_downloaded

If TRUE(default) and a URL was provided, cache the downloaded files in session for an easy reuse.

Import data from IPC file(s)

Description

read_ipc_polars() imports the data as a Polars DataFrame.

scan_ipc_polars() imports the data as a Polars LazyFrame.

Usage

read_ipc_polars(
  source,
  ...,
  n_rows = NULL,
  memory_map = TRUE,
  row_index_name = NULL,
  row_index_offset = 0L,
  rechunk = FALSE,
  cache = TRUE,
  include_file_paths = NULL
)

scan_ipc_polars(
  source,
  ...,
  n_rows = NULL,
  memory_map = TRUE,
  row_index_name = NULL,
  row_index_offset = 0L,
  rechunk = FALSE,
  cache = TRUE,
  include_file_paths = NULL
)

Arguments

source

Path to a file. You can use globbing with * to scan/read multiple files in the same directory (see examples).
...

Ignored.
n_rows

Maximum number of rows to read.
memory_map

A logical. If TRUE, try to memory map the file. This can greatly improve performance on repeated queries as the OS may cache pages. Only uncompressed Arrow IPC files can be memory mapped.
row_index_name

If not NULL, this will insert a row index column with the given name into the DataFrame.
row_index_offset

Offset to start the row index column (only used if the name is set).
rechunk

In case of reading multiple files via a glob pattern, rechunk the final DataFrame into contiguous memory chunks.
cache

Cache the result after reading.
include_file_paths

Character value indicating the column name that will include the path of the source file(s).

Details

Hive-style partitioning is not supported yet.

Import data from NDJSON file(s)

Description

read_ndjson_polars() imports the data as a Polars DataFrame.

scan_ndjson_polars() imports the data as a Polars LazyFrame.

Usage

read_ndjson_polars(
  source,
  ...,
  infer_schema_length = 100,
  batch_size = NULL,
  n_rows = NULL,
  low_memory = FALSE,
  rechunk = FALSE,
  row_index_name = NULL,
  row_index_offset = 0,
  reuse_downloaded = TRUE,
  ignore_errors = FALSE
)

scan_ndjson_polars(
  source,
  ...,
  infer_schema_length = 100,
  batch_size = NULL,
  n_rows = NULL,
  low_memory = FALSE,
  rechunk = FALSE,
  row_index_name = NULL,
  row_index_offset = 0,
  reuse_downloaded = TRUE,
  ignore_errors = FALSE
)

Arguments

source

Path to a file or URL. It is possible to provide multiple paths provided that all NDJSON files have the same schema. It is not possible to provide several URLs.
...

Ignored.
infer_schema_length

Maximum number of rows to read to infer the column types. If set to 0, all columns will be read as UTF-8. If NULL, a full table scan will be done (slow).
batch_size

Number of rows that will be processed per thread.
n_rows

Maximum number of rows to read.
low_memory

Reduce memory usage (will yield a lower performance).
rechunk

Reallocate to contiguous memory when all chunks / files are parsed.
row_index_name

If not NULL, this will insert a row index column with the given name into the DataFrame.
row_index_offset

Offset to start the row index column (only used if the name is set).
reuse_downloaded

If TRUE(default) and a URL was provided, cache the downloaded files in session for an easy reuse.
ignore_errors

Keep reading the file even if some lines yield errors. You can also use infer_schema_length = 0 to read all columns as UTF8 to check which values might cause an issue.

Import data from Parquet file(s)

Description

read_parquet_polars() imports the data as a Polars DataFrame.

scan_parquet_polars() imports the data as a Polars LazyFrame.

Usage

read_parquet_polars(
  source,
  ...,
  n_rows = NULL,
  row_index_name = NULL,
  row_index_offset = 0L,
  parallel = "auto",
  hive_partitioning = NULL,
  hive_schema = NULL,
  try_parse_hive_dates = TRUE,
  glob = TRUE,
  rechunk = TRUE,
  low_memory = FALSE,
  storage_options = NULL,
  use_statistics = TRUE,
  cache = TRUE,
  include_file_paths = NULL
)

scan_parquet_polars(
  source,
  ...,
  n_rows = NULL,
  row_index_name = NULL,
  row_index_offset = 0L,
  parallel = "auto",
  hive_partitioning = NULL,
  hive_schema = NULL,
  try_parse_hive_dates = TRUE,
  glob = TRUE,
  rechunk = FALSE,
  low_memory = FALSE,
  storage_options = NULL,
  use_statistics = TRUE,
  cache = TRUE,
  include_file_paths = NULL
)

Arguments

source

Path to a file. You can use globbing with * to scan/read multiple files in the same directory (see examples).
...

Ignored.
n_rows

Maximum number of rows to read.
row_index_name

If not NULL, this will insert a row index column with the given name into the DataFrame.
row_index_offset

Offset to start the row index column (only used if the name is set).
parallel

This determines the direction of parallelism. "auto" will try to determine the optimal direction. Can be "auto", "columns", "row_groups", "prefiltered", or "none". See 'Details'.
hive_partitioning

Infer statistics and schema from Hive partitioned URL and use them to prune reads. If NULL (default), it is automatically enabled when a single directory is passed, and otherwise disabled.
hive_schema

A list containing the column names and data types of the columns by which the data is partitioned, e.g. list(a = pl$String, b = pl$Float32). If NULL (default), the schema of the Hive partitions is inferred.
try_parse_hive_dates

Whether to try parsing hive values as date/datetime types.
glob

Expand path given via globbing rules.
rechunk

In case of reading multiple files via a glob pattern, rechunk the final DataFrame into contiguous memory chunks.
low_memory

Reduce memory usage (will yield a lower performance).
storage_options

Experimental. List of options necessary to scan parquet files from different cloud storage providers (GCP, AWS, Azure, HuggingFace). See the 'Details' section.
use_statistics

Use statistics in the parquet file to determine if pages can be skipped from reading.
cache

Cache the result after reading.
include_file_paths

Include the path of the source file(s) as a column with this name.

Details

On parallel strategies

The prefiltered strategy first evaluates the pushed-down predicates in parallel and determines a mask of which rows to read. Then, it parallelizes over both the columns and the row groups while filtering out rows that do not need to be read. This can provide significant speedups for large files (i.e. many row-groups) with a predicate that filters clustered rows or filters heavily. In other cases, prefiltered may slow down the scan compared other strategies.

The prefiltered settings falls back to auto if no predicate is given.

Connecting to cloud providers

Polars supports scanning parquet files from different cloud providers. The cloud providers currently supported are AWS, GCP, and Azure. The supported keys to pass to the storage_options argument can be found here:

Currently it is impossible to scan public parquet files from GCP without a valid service account. Be sure to always include a service account in the storage_options argument.

Scanning from HuggingFace

It is possible to scan data stored on HuggingFace using a path starting with ⁠hf://⁠. The ⁠hf://⁠ path format is defined as ⁠hf://BUCKET/REPOSITORY@REVISION/PATH⁠, where:

  • BUCKET is one of datasets or spaces

  • REPOSITORY is the location of the repository. this is usually in the format of username/repo_name. A branch can also be optionally specified by appending ⁠@branch⁠.

  • REVISION is the name of the branch (or commit) to use. This is optional and defaults to main if not given.

  • PATH is a file or directory path, or a glob pattern from the repository root.

A Hugging Face API key can be passed to access private locations using either of the following methods:

  • Passing a token in storage_options to the scan function, e.g. ⁠scan_parquet(..., storage_options = list(token = <your HF token>))⁠

  • Setting the HF_TOKEN environment variable, e.g. ⁠Sys.setenv(HF_TOKEN = <your HF token>)⁠.

Group by one or more variables

Description

Most data operations are done on groups defined by variables. group_by() takes an existing Polars Data/LazyFrame and converts it into a grouped one where operations are performed "by group". ungroup() removes grouping.

Usage

## S3 method for class 'RPolarsDataFrame'
group_by(.data, ..., maintain_order = FALSE, .add = FALSE)

## S3 method for class 'RPolarsDataFrame'
ungroup(x, ...)

## S3 method for class 'RPolarsLazyFrame'
group_by(.data, ..., maintain_order = FALSE, .add = FALSE)

## S3 method for class 'RPolarsLazyFrame'
ungroup(x, ...)

Arguments

.data

A Polars Data/LazyFrame
...

Variables to group by (used in group_by() only). Not used in ungroup().
maintain_order

Maintain row order. For performance reasons, this is FALSE by default). Setting it to TRUE can slow down the process with large datasets and prevents the use of streaming.
.add

When FALSE (default), group_by() will override existing groups. To add to the existing groups, use .add = TRUE.
x

A Polars Data/LazyFrame

Examples

by_cyl <- mtcars |>
  as_polars_df() |>
  group_by(cyl)

by_cyl

by_cyl |> summarise(
  disp = mean(disp),
  hp = mean(hp)
)
by_cyl |> filter(disp == max(disp))

Grouping metadata

Description

group_vars() returns a character vector with the names of the grouping variables. group_keys() returns a data frame with one row per group.

Usage

## S3 method for class 'RPolarsDataFrame'
group_split(.tbl, ..., .keep = TRUE)

Arguments

.tbl

A Polars Data/LazyFrame
...

If .tbl is not grouped, variables to group by. If .tbl is already grouped, this is ignored.
.keep

Should the grouping columns be kept?

Examples

pl_g <- polars::as_polars_df(iris) |>
  group_by(Species)

group_split(pl_g)

Grouping metadata

Description

group_vars() returns a character vector with the names of the grouping variables. group_keys() returns a data frame with one row per group.

Usage

## S3 method for class 'RPolarsDataFrame'
group_vars(x)

## S3 method for class 'RPolarsLazyFrame'
group_vars(x)

## S3 method for class 'RPolarsDataFrame'
group_keys(.tbl, ...)

## S3 method for class 'RPolarsLazyFrame'
group_keys(.tbl, ...)

Arguments

x, .tbl

A Polars Data/LazyFrame
...

Not used.

Examples

pl_g <- polars::as_polars_df(mtcars) |>
  group_by(cyl, am)

group_vars(pl_g)

group_keys(pl_g)

Mutating joins

Description

Mutating joins add columns from y to x, matching observations based on the keys.

Usage

## S3 method for class 'RPolarsDataFrame'
left_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsDataFrame'
right_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsDataFrame'
full_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsDataFrame'
inner_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsLazyFrame'
left_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsLazyFrame'
right_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsLazyFrame'
full_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

## S3 method for class 'RPolarsLazyFrame'
inner_join(
  x,
  y,
  by = NULL,
  copy = NULL,
  suffix = c(".x", ".y"),
  ...,
  keep = NULL,
  na_matches = "na",
  relationship = NULL
)

Arguments

x, y

Two Polars Data/LazyFrames
by

Variables to join by. If NULL (default), ⁠*_join()⁠ will perform a natural join, using all variables in common across x and y. A message lists the variables so that you can check they're correct; suppress the message by supplying by explicitly.

by can take a character vector, like c("x", "y") if x and y are in both datasets. To join on variables that don't have the same name, use equalities in the character vector, like c("x1" = "x2", "y"). If you use a character vector, the join can only be done using strict equality.

by can also be a specification created by dplyr::join_by(). Contrary to the input as character vector shown above, join_by() uses unquoted column names, e.g join_by(x1 == x2, y).

Finally, inner_join() also supports inequality joins, e.g. join_by(x1 >= x2), and the helpers between(), overlaps(), and within(). See the documentation of dplyr::join_by() for more information. Other join types will likely support inequality joins in the future.
copy, keep

Not used.
suffix

If there are non-joined duplicate variables in x and y, these suffixes will be added to the output to disambiguate them. Should be a character vector of length 2.
...

Not used.
na_matches

Should two NA values match?

  • "na", the default, treats two NA values as equal.

  • "never" treats two NA values as different and will never match them together or to any other values.

Note that when joining Polars Data/LazyFrames, NaN are always considered equal, no matter the value of na_matches. This differs from the original dplyr implementation.
relationship

Handling of the expected relationship between the keys of x and y. Must be one of the following:

  • NULL, the default, is equivalent to "many-to-many". It doesn't expect any relationship between x and y.

  • "one-to-one" expects each row in x to match at most 1 row in y and each row in y to match at most 1 row in x.

  • "one-to-many" expects each row in y to match at most 1 row in x.

  • "many-to-one" expects each row in x matches at most 1 row in y.

Examples

test <- polars::pl$DataFrame(
  x = c(1, 2, 3),
  y1 = c(1, 2, 3),
  z = c(1, 2, 3)
)

test2 <- polars::pl$DataFrame(
  x = c(1, 2, 4),
  y2 = c(1, 2, 4),
  z2 = c(4, 5, 7)
)

test

test2

# default is to use common columns, here "x" only
left_join(test, test2)

# we can specify the columns on which to join with join_by()...
left_join(test, test2, by = join_by(x, y1 == y2))

# ... or with a character vector
left_join(test, test2, by = c("x", "y1" = "y2"))

# we can customize the suffix of common column names not used to join
test2 <- polars::pl$DataFrame(
  x = c(1, 2, 4),
  y1 = c(1, 2, 4),
  z = c(4, 5, 7)
)

left_join(test, test2, by = "x", suffix = c("_left", "_right"))

# the argument "relationship" ensures the join matches the expectation
country <- polars::pl$DataFrame(
  iso = c("FRA", "DEU"),
  value = 1:2
)
country

country_year <- polars::pl$DataFrame(
  iso = rep(c("FRA", "DEU"), each = 2),
  year = rep(2019:2020, 2),
  value2 = 3:6
)
country_year

# We expect that each row in "x" matches only one row in "y" but, it's not
# true as each row of "x" matches two rows of "y"
tryCatch(
  left_join(country, country_year, join_by(iso), relationship = "one-to-one"),
  error = function(e) e
)

# A correct expectation would be "one-to-many":
left_join(country, country_year, join_by(iso), relationship = "one-to-many")

Create a column with unique id per row values

Description

Create a column with unique id per row values

Usage

make_unique_id(.data, ..., new_col = "hash")

Arguments

.data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
new_col

Name of the new column

Examples

mtcars |>
  as_polars_df() |>
  make_unique_id(am, gear)

Create, modify, and delete columns

Description

This creates new columns that are functions of existing variables. It can also modify (if the name is the same as an existing column) and delete columns (by setting their value to NULL).

Usage

## S3 method for class 'RPolarsDataFrame'
mutate(.data, ..., .by = NULL, .keep = c("all", "used", "unused", "none"))

## S3 method for class 'RPolarsLazyFrame'
mutate(.data, ..., .by = NULL, .keep = c("all", "used", "unused", "none"))

Arguments

.data

A Polars Data/LazyFrame
...

Name-value pairs. The name gives the name of the column in the output. The value can be:

  • A vector the same length as the current group (or the whole data frame if ungrouped).

  • NULL, to remove the column.

across() is mostly supported, except in a few cases. In particular, if the .cols argument is where(...), it will not select variables that were created before across(). Other select helpers are supported. See the examples.
.by

Optionally, a selection of columns to group by for just this operation, functioning as an alternative to group_by(). The group order is not maintained, use group_by() if you want more control over it.
.keep

Control which columns from .data are retained in the output. Grouping columns and columns created by ... are always kept.

  • "all" retains all columns from .data. This is the default.

  • "used" retains only the columns used in ... to create new columns. This is useful for checking your work, as it displays inputs and outputs side-by- side.

  • "unused" retains only the columns not used in ... to create new columns. This is useful if you generate new columns, but no longer need the columns used to generate them.

  • "none" doesn't retain any extra columns from .data. Only the grouping variables and columns created by ... are kept.

Details

A lot of functions available in base R (cos, mean, multiplying, etc.) or in other packages (dplyr::lag(), etc.) are implemented in an efficient way in Polars. These functions are automatically translated to Polars syntax under the hood so that you can continue using the classic R syntax and functions.

If a Polars built-in replacement doesn't exist (for example for custom functions), then tidypolars will throw an error. See the vignette on Polars expressions to know how to write custom functions that are accepted by tidypolars.

Examples

pl_iris <- polars::as_polars_df(iris)

# classic operation
mutate(pl_iris, x = Sepal.Width + Sepal.Length)

# logical operation
mutate(pl_iris, x = Sepal.Width > Sepal.Length & Petal.Width > Petal.Length)

# overwrite existing variable
mutate(pl_iris, Sepal.Width = Sepal.Width * 2)

# grouped computation
pl_iris |>
  group_by(Species) |>
  mutate(foo = mean(Sepal.Length))

# an alternative syntax for grouping is to use `.by`
pl_iris |>
  mutate(foo = mean(Sepal.Length), .by = Species)

# across() is available
pl_iris |>
  mutate(
    across(.cols = contains("Sepal"), .fns = mean, .names = "{.fn}_of_{.col}")
  )
#
# It can receive several types of functions:
pl_iris |>
  mutate(
    across(
      .cols = contains("Sepal"),
      .fns = list(mean = mean, sd = ~ sd(.x)),
      .names = "{.fn}_of_{.col}"
    )
  )

# Be careful when using across(.cols = where(...), ...) as it will not include
# variables created in the same `...` (this is only the case for `where()`):
## Not run: 
pl_iris |>
  mutate(
    foo = 1,
    across(
      .cols = where(is.numeric),
      \(x) x - 1000 # <<<<<<<<< this will not be applied on variable "foo"
    )
  )

## End(Not run)
# Warning message:
# In `across()`, the argument `.cols = where(is.numeric)` will not take into account
# variables created in the same `mutate()`/`summarize` call.

# Embracing an external variable works
some_value <- 1
mutate(pl_iris, x = {{ some_value }})

Pivot a Data/LazyFrame from wide to long

Description

Pivot a Data/LazyFrame from wide to long

Usage

## S3 method for class 'RPolarsDataFrame'
pivot_longer(
  data,
  cols,
  ...,
  names_to = "name",
  names_prefix = NULL,
  values_to = "value"
)

## S3 method for class 'RPolarsLazyFrame'
pivot_longer(
  data,
  cols,
  ...,
  names_to = "name",
  names_prefix = NULL,
  values_to = "value"
)

Arguments

data

A Polars Data/LazyFrame
cols

Columns to pivot into longer format. Can be anything accepted by dplyr::select().
...

Not used.
names_to

The (quoted) name of the column that will contain the column names specified by cols.
names_prefix

A regular expression used to remove matching text from the start of each variable name.
values_to

A string specifying the name of the column to create from the data stored in cell values.

Examples

pl_relig_income <- polars::pl$DataFrame(tidyr::relig_income)
pl_relig_income

pl_relig_income |>
  pivot_longer(!religion, names_to = "income", values_to = "count")

pl_billboard <- polars::pl$DataFrame(tidyr::billboard)
pl_billboard

pl_billboard |>
  pivot_longer(
    cols = starts_with("wk"),
    names_to = "week",
    names_prefix = "wk",
    values_to = "rank",
  )

Pivot a DataFrame from long to wide

Description

Pivot a DataFrame from long to wide

Usage

## S3 method for class 'RPolarsDataFrame'
pivot_wider(
  data,
  ...,
  id_cols = NULL,
  names_from = name,
  values_from = value,
  names_prefix = "",
  names_sep = "_",
  names_glue = NULL,
  values_fill = NULL
)

Arguments

data

A Polars DataFrame (LazyFrames are not supported).
...

Not used.
id_cols

A set of columns that uniquely identify each observation. Typically used when you have redundant variables, i.e. variables whose values are perfectly correlated with existing variables.

Defaults to all columns in data except for the columns specified through names_from and values_from. If a tidyselect expression is supplied, it will be evaluated on data after removing the columns specified through names_from and values_from.
names_from

The (quoted or unquoted) column names whose values will be used for the names of the new columns.
values_from

The (quoted or unquoted) column names whose values will be used to fill the new columns.
names_prefix

String added to the start of every variable name. This is particularly useful if names_from is a numeric vector and you want to create syntactic variable names.
names_sep

If names_from or values_from contains multiple variables, this will be used to join their values together into a single string to use as a column name.
names_glue

Instead of names_sep and names_prefix, you can supply a glue specification that uses the names_from columns to create custom column names.
values_fill

A scalar that will be used to replace missing values in the new columns. Note that the type of this value will be applied to new columns. For example, if you provide a character value to fill numeric columns, then all these columns will be converted to character.

Examples

pl_fish_encounters <- polars::pl$DataFrame(tidyr::fish_encounters)

pl_fish_encounters |>
  pivot_wider(names_from = station, values_from = seen)

pl_fish_encounters |>
  pivot_wider(names_from = station, values_from = seen, values_fill = 0)

# be careful about the type of the replacement value!
pl_fish_encounters |>
  pivot_wider(names_from = station, values_from = seen, values_fill = "a")

# using "names_glue" to specify the names of new columns
production <- expand.grid(
  product = c("A", "B"),
  country = c("AI", "EI"),
  year = 2000:2014
) |>
  filter((product == "A" & country == "AI") | product == "B") |>
  mutate(production = 1:45) |>
  as_polars_df()

production

production |>
  pivot_wider(
    names_from = c(product, country),
    values_from = production,
    names_glue = "prod_{product}_{country}"
  )

Extract a variable of a Data/LazyFrame

Description

This returns an R vector and not a Polars Series.

Usage

## S3 method for class 'RPolarsDataFrame'
pull(.data, var, ...)

## S3 method for class 'RPolarsLazyFrame'
pull(.data, var, ...)

Arguments

.data

A Polars Data/LazyFrame
var

A quoted or unquoted variable name, or a variable index.
...

Not used.

Examples

pl_test <- as_polars_df(iris)
pull(pl_test, Sepal.Length)
pull(pl_test, "Sepal.Length")

Change column order

Description

Use relocate() to change column positions, using the same syntax as select() to make it easy to move blocks of columns at once.

Usage

## S3 method for class 'RPolarsDataFrame'
relocate(.data, ..., .before = NULL, .after = NULL)

## S3 method for class 'RPolarsLazyFrame'
relocate(.data, ..., .before = NULL, .after = NULL)

Arguments

.data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
.before, .after

Column name (either quoted or unquoted) that indicates the destination of columns selected by .... Supplying neither will move columns to the left-hand side; specifying both is an error.

Examples

dat <- as_polars_df(mtcars)

dat |>
  relocate(hp, vs, .before = cyl)

# if .before and .after are not specified, selected columns are moved to the
# first positions
dat |>
  relocate(hp, vs)

# .before and .after can be quoted or unquoted
dat |>
  relocate(hp, vs, .after = "gear")

# select helpers are also available
dat |>
  relocate(contains("[aeiou]"))

dat |>
  relocate(hp, vs, .after = last_col())

Rename columns

Description

Rename columns

Usage

## S3 method for class 'RPolarsDataFrame'
rename(.data, ...)

## S3 method for class 'RPolarsLazyFrame'
rename(.data, ...)

## S3 method for class 'RPolarsDataFrame'
rename_with(.data, .fn, .cols = tidyselect::everything(), ...)

## S3 method for class 'RPolarsLazyFrame'
rename_with(.data, .fn, .cols = tidyselect::everything(), ...)

Arguments

.data

A Polars Data/LazyFrame
...

For rename(), use new_name = old_name to rename selected variables. It is also possible to use quotation marks, e.g "new_name" = "old_name".

For rename_with, additional arguments passed to fn.
.fn

Function to apply on column names
.cols

Columns on which to apply fn. Can be anything accepted by dplyr::select().

Examples

pl_test <- polars::as_polars_df(mtcars)

rename(pl_test, miles_per_gallon = mpg, horsepower = "hp")

rename(pl_test, `Miles per gallon` = "mpg", `Horse power` = "hp")

rename_with(pl_test, toupper, .cols = contains("p"))

pl_test_2 <- polars::as_polars_df(iris)

rename_with(pl_test_2, function(x) tolower(gsub(".", "_", x, fixed = TRUE)))

rename_with(pl_test_2, \(x) tolower(gsub(".", "_", x, fixed = TRUE)))

Replace NAs with specified values

Description

Replace NAs with specified values

Usage

## S3 method for class 'RPolarsDataFrame'
replace_na(data, replace, ...)

## S3 method for class 'RPolarsLazyFrame'
replace_na(data, replace, ...)

Arguments

data

A Polars Data/LazyFrame
replace

Either a scalar that will be used to replace NA in all columns, or a named list with the column name and the value that will be used to replace NA in it.
...

Not used.

Examples

pl_test <- polars::pl$DataFrame(x = c(NA, 1), y = c(2, NA))

# replace all NA with 0
replace_na(pl_test, 0)

# custom replacement per column
replace_na(pl_test, list(x = 0, y = 999))

Group input by rows

Description

[EXPERIMENTAL]

rowwise() allows you to compute on a Data/LazyFrame a row-at-a-time. This is most useful when a vectorised function doesn't exist. rowwise() produces another type of grouped data, and therefore can be removed with ungroup().

Usage

## S3 method for class 'RPolarsDataFrame'
rowwise(data, ...)

## S3 method for class 'RPolarsLazyFrame'
rowwise(data, ...)

Arguments

data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.

Value

A Polars Data/LazyFrame.

Examples

df <- polars::pl$DataFrame(x = c(1, 3, 4), y = c(2, 1, 5), z = c(2, 3, 1))

# Compute the mean of x, y, z in each row
df |>
 rowwise() |>
 mutate(m = mean(c(x, y, z)))

# Compute the min and max of x and y in each row
df |>
 rowwise() |>
 mutate(min = min(c(x, y)), max = max(c(x, y)))

Select columns from a Data/LazyFrame

Description

Select columns from a Data/LazyFrame

Usage

## S3 method for class 'RPolarsDataFrame'
select(.data, ...)

## S3 method for class 'RPolarsLazyFrame'
select(.data, ...)

Arguments

.data

A Polars Data/LazyFrame
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc. Renaming is also possible.

Examples

pl_iris <- polars::as_polars_df(iris)

select(pl_iris, c("Sepal.Length", "Sepal.Width"))
select(pl_iris, Sepal.Length, Sepal.Width)
select(pl_iris, 1:3)
select(pl_iris, starts_with("Sepal"))
select(pl_iris, -ends_with("Length"))

# Renaming while selecting is also possible
select(pl_iris, foo1 = Sepal.Length, Sepal.Width)

Filtering joins

Description

Filtering joins filter rows from x based on the presence or absence of matches in y:

  • semi_join() return all rows from x with a match in y.

  • anti_join() return all rows from x without a match in y.

Usage

## S3 method for class 'RPolarsDataFrame'
semi_join(x, y, by = NULL, ..., na_matches = "na")

## S3 method for class 'RPolarsDataFrame'
anti_join(x, y, by = NULL, ..., na_matches = "na")

## S3 method for class 'RPolarsLazyFrame'
semi_join(x, y, by = NULL, ..., na_matches = "na")

## S3 method for class 'RPolarsLazyFrame'
anti_join(x, y, by = NULL, ..., na_matches = "na")

Arguments

x, y

Two Polars Data/LazyFrames
by

Variables to join by. If NULL (default), ⁠*_join()⁠ will perform a natural join, using all variables in common across x and y. A message lists the variables so that you can check they're correct; suppress the message by supplying by explicitly.

by can take a character vector, like c("x", "y") if x and y are in both datasets. To join on variables that don't have the same name, use equalities in the character vector, like c("x1" = "x2", "y"). If you use a character vector, the join can only be done using strict equality.

by can also be a specification created by dplyr::join_by(). Contrary to the input as character vector shown above, join_by() uses unquoted column names, e.g join_by(x1 == x2, y).

Finally, inner_join() also supports inequality joins, e.g. join_by(x1 >= x2), and the helpers between(), overlaps(), and within(). See the documentation of dplyr::join_by() for more information. Other join types will likely support inequality joins in the future.
...

Not used.
na_matches

Should two NA values match?

  • "na", the default, treats two NA values as equal.

  • "never" treats two NA values as different and will never match them together or to any other values.

Note that when joining Polars Data/LazyFrames, NaN are always considered equal, no matter the value of na_matches. This differs from the original dplyr implementation.

Examples

test <- polars::pl$DataFrame(
  x = c(1, 2, 3),
  y = c(1, 2, 3),
  z = c(1, 2, 3)
)

test2 <- polars::pl$DataFrame(
  x = c(1, 2, 4),
  y = c(1, 2, 4),
  z2 = c(1, 2, 4)
)

test

test2

# only keep the rows of `test` that have matching keys in `test2`
semi_join(test, test2, by = c("x", "y"))

# only keep the rows of `test` that don't have matching keys in `test2`
anti_join(test, test2, by = c("x", "y"))

Separate a character column into multiple columns based on a substring

Description

Currently, splitting a column on a regular expression or position is not possible.

Usage

## S3 method for class 'RPolarsDataFrame'
separate(data, col, into, sep = " ", remove = TRUE, ...)

## S3 method for class 'RPolarsLazyFrame'
separate(data, col, into, sep = " ", remove = TRUE, ...)

Arguments

data

A Polars Data/LazyFrame
col

Column to split
into

Character vector containing the names of new variables to create. Use NA to omit the variable in the output.
sep

String that is used to split the column. Regular expressions are not supported yet.
remove

If TRUE, remove input column from output data frame.
...

Not used.

Examples

test <- polars::pl$DataFrame(
  x = c(NA, "x.y", "x.z", "y.z")
)
separate(test, x, into = c("foo", "foo2"), sep = ".")

Stream output to a CSV file

Description

This function allows to stream a LazyFrame that is larger than RAM directly to a .csv file without collecting it in the R session, thus preventing crashes because of too small memory.

Usage

sink_csv(
  .data,
  path,
  ...,
  include_bom = FALSE,
  include_header = TRUE,
  separator = ",",
  line_terminator = "\n",
  quote = "\"",
  batch_size = 1024,
  datetime_format = NULL,
  date_format = NULL,
  time_format = NULL,
  float_precision = NULL,
  null_values = "",
  quote_style = "necessary",
  maintain_order = TRUE,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  no_optimization = FALSE
)

Arguments

.data

A Polars LazyFrame.
path

Output file (must be a .csv file).
...

Ignored.
include_bom

Whether to include UTF-8 BOM (byte order mark) in the CSV output.
include_header

Whether to include header in the CSV output.
separator

Separate CSV fields with this symbol.
line_terminator

String used to end each row.
quote

Byte to use as quoting character.
batch_size

Number of rows that will be processed per thread.
datetime_format, date_format, time_format

A format string used to format date and time values. See ?strptime() for accepted values. If no format specified, the default fractional-second precision is inferred from the maximum time unit found in the Datetime cols (if any).
float_precision

Number of decimal places to write, applied to both Float32 and Float64 datatypes.
null_values

A string representing null values (defaulting to the empty string).
quote_style

Determines the quoting strategy used:

  • "necessary" (default): This puts quotes around fields only when necessary. They are necessary when fields contain a quote, delimiter or record terminator. Quotes are also necessary when writing an empty record (which is indistinguishable from a record with one empty field).

  • "always": This puts quotes around every field.

  • "non_numeric": This puts quotes around all fields that are non-numeric. Namely, when writing a field that does not parse as a valid float or integer, then quotes will be used even if they aren't strictly necessary.

maintain_order

Whether maintain the order the data was processed (default is TRUE). Setting this to FALSE will be slightly faster.
type_coercion

Coerce types such that operations succeed and run on minimal required memory (default is TRUE).
predicate_pushdown

Applies filters as early as possible at scan level (default is TRUE).
projection_pushdown

Select only the columns that are needed at the scan level (default is TRUE).
simplify_expression

Various optimizations, such as constant folding and replacing expensive operations with faster alternatives (default is TRUE).
slice_pushdown

Only load the required slice from the scan. Don't materialize sliced outputs level. Don't materialize sliced outputs (default is TRUE).
no_optimization

Sets the following optimizations to FALSE: predicate_pushdown, projection_pushdown, slice_pushdown, simplify_expression. Default is FALSE.

Value

The input LazyFrame.

Examples

## Not run: 
# This is an example workflow where sink_csv() is not very useful because
# the data would fit in memory. It simply is an example of using it at the
# end of a piped workflow.

# Create files for the CSV input and output:
file_csv <- tempfile(fileext = ".csv")
file_csv2 <- tempfile(fileext = ".csv")

# Write some data in a CSV file
fake_data <- do.call("rbind", rep(list(mtcars), 1000))
write.csv(fake_data, file = file_csv, row.names = FALSE)

# In a new R session, we could read this file as a LazyFrame, do some operations,
# and write it to another CSV file without ever collecting it in the R session:
scan_csv_polars(file_csv) |>
  filter(cyl %in% c(4, 6), mpg > 22) |>
  mutate(
    hp_gear_ratio = hp / gear
  ) |>
  sink_csv(path = file_csv2)


## End(Not run)

Stream output to an IPC file

Description

This function allows to stream a LazyFrame that is larger than RAM directly to an IPC file without collecting it in the R session, thus preventing crashes because of too small memory.

Usage

sink_ipc(
  .data,
  path,
  ...,
  compression = "zstd",
  maintain_order = TRUE,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  no_optimization = FALSE
)

Arguments

.data

A Polars LazyFrame.
path

Output file.
...

Ignored.
compression

NULL or a character of the compression method, "uncompressed" or "lz4" or "zstd". NULL is equivalent to "uncompressed". Choose "zstd" for good compression performance. Choose "lz4" for fast compression/decompression.
maintain_order

Whether maintain the order the data was processed (default is TRUE). Setting this to FALSE will be slightly faster.
type_coercion

Coerce types such that operations succeed and run on minimal required memory (default is TRUE).
predicate_pushdown

Applies filters as early as possible at scan level (default is TRUE).
projection_pushdown

Select only the columns that are needed at the scan level (default is TRUE).
simplify_expression

Various optimizations, such as constant folding and replacing expensive operations with faster alternatives (default is TRUE).
slice_pushdown

Only load the required slice from the scan. Don't materialize sliced outputs level. Don't materialize sliced outputs (default is TRUE).
no_optimization

Sets the following optimizations to FALSE: predicate_pushdown, projection_pushdown, slice_pushdown, simplify_expression. Default is FALSE.

Value

The input LazyFrame.

Stream output to a NDJSON file

Description

This writes the output of a query directly to a NDJSON file without collecting it in the R session first. This is useful if the output of the query is still larger than RAM as it would crash the R session if it was collected into R.

Usage

sink_ndjson(
  .data,
  path,
  ...,
  maintain_order = TRUE,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  no_optimization = FALSE
)

Arguments

.data

A Polars LazyFrame.
path

Output file.
...

Ignored.
maintain_order

Whether maintain the order the data was processed (default is TRUE). Setting this to FALSE will be slightly faster.
type_coercion

Coerce types such that operations succeed and run on minimal required memory (default is TRUE).
predicate_pushdown

Applies filters as early as possible at scan level (default is TRUE).
projection_pushdown

Select only the columns that are needed at the scan level (default is TRUE).
simplify_expression

Various optimizations, such as constant folding and replacing expensive operations with faster alternatives (default is TRUE).
slice_pushdown

Only load the required slice from the scan. Don't materialize sliced outputs level. Don't materialize sliced outputs (default is TRUE).
no_optimization

Sets the following optimizations to FALSE: predicate_pushdown, projection_pushdown, slice_pushdown, simplify_expression. Default is FALSE.

Value

The input LazyFrame.

Stream output to a parquet file

Description

This function allows to stream a LazyFrame that is larger than RAM directly to a .parquet file without collecting it in the R session, thus preventing crashes because of too small memory.

Usage

sink_parquet(
  .data,
  path,
  ...,
  compression = "zstd",
  compression_level = 3,
  statistics = FALSE,
  row_group_size = NULL,
  data_page_size = NULL,
  maintain_order = TRUE,
  type_coercion = TRUE,
  predicate_pushdown = TRUE,
  projection_pushdown = TRUE,
  simplify_expression = TRUE,
  slice_pushdown = TRUE,
  no_optimization = FALSE
)

Arguments

.data

A Polars LazyFrame.
path

Output file (must be a .parquet file).
...

Ignored.
compression

The compression method. One of :

  • "uncompressed"

  • "zstd" (default): good compression performance

  • "lz4": fast compression / decompression

  • "snappy": more backwards compatibility guarantees when you deal with older parquet readers.

  • "gzip", "lzo", "brotli"

compression_level

The level of compression to use (default is 3). Only used if compression is one of "gzip", "brotli", or "zstd". Higher compression means smaller files on disk.

  • "gzip" : min-level = 0, max-level = 10

  • "brotli" : min-level = 0, max-level = 11

  • "zstd" : min-level = 1, max-level = 22.

statistics

Whether to compute and write column statistics (default is FALSE). This requires more computations.
row_group_size

Size of the row groups in number of rows. If NULL (default), the chunks of the DataFrame are used. Writing in smaller chunks may reduce memory pressure and improve writing speeds.
data_page_size

If NULL (default), the limit will be around 1MB.
maintain_order

Whether maintain the order the data was processed (default is TRUE). Setting this to FALSE will be slightly faster.
type_coercion

Coerce types such that operations succeed and run on minimal required memory (default is TRUE).
predicate_pushdown

Applies filters as early as possible at scan level (default is TRUE).
projection_pushdown

Select only the columns that are needed at the scan level (default is TRUE).
simplify_expression

Various optimizations, such as constant folding and replacing expensive operations with faster alternatives (default is TRUE).
slice_pushdown

Only load the required slice from the scan. Don't materialize sliced outputs level. Don't materialize sliced outputs (default is TRUE).
no_optimization

Sets the following optimizations to FALSE: predicate_pushdown, projection_pushdown, slice_pushdown, simplify_expression. Default is FALSE.

Value

The input LazyFrame.

Examples

## Not run: 
# This is an example workflow where sink_parquet() is not very useful because
# the data would fit in memory. It simply is an example of using it at the
# end of a piped workflow.

# Create files for the CSV input and the Parquet output:
file_csv <- tempfile(fileext = ".csv")
file_parquet <- tempfile(fileext = ".parquet")

# Write some data in a CSV file
fake_data <- do.call("rbind", rep(list(mtcars), 1000))
write.csv(fake_data, file = file_csv, row.names = FALSE)

# In a new R session, we could read this file as a LazyFrame, do some operations,
# and write it to a parquet file without ever collecting it in the R session:
scan_csv_polars(file_csv) |>
  filter(cyl %in% c(4, 6), mpg > 22) |>
  mutate(
    hp_gear_ratio = hp / gear
  ) |>
  sink_parquet(path = file_parquet)


## End(Not run)

Subset rows of a Data/LazyFrame

Description

Subset rows of a Data/LazyFrame

Usage

## S3 method for class 'RPolarsDataFrame'
slice_tail(.data, ..., n, by = NULL)

## S3 method for class 'RPolarsLazyFrame'
slice_tail(.data, ..., n, by = NULL)

## S3 method for class 'RPolarsDataFrame'
slice_head(.data, ..., n, by = NULL)

## S3 method for class 'RPolarsLazyFrame'
slice_head(.data, ..., n, by = NULL)

## S3 method for class 'RPolarsDataFrame'
slice_sample(.data, ..., n = NULL, prop = NULL, replace = FALSE, by = NULL)

Arguments

.data

A Polars Data/LazyFrame
...

Not used.
n

The number of rows to select from the start or the end of the data. Cannot be used with prop.
by

Optionally, a selection of columns to group by for just this operation, functioning as an alternative to group_by(). The group order is not maintained, use group_by() if you want more control over it.
prop

Proportion of rows to select. Cannot be used with n.
replace

Perform the sampling with replacement (TRUE) or without (FALSE).

Examples

pl_test <- polars::as_polars_df(iris)
slice_head(pl_test, n = 3)
slice_tail(pl_test, n = 3)
slice_sample(pl_test, n = 5)
slice_sample(pl_test, prop = 0.1)

Summarize each group down to one row

Description

summarize() returns one row for each combination of grouping variables (one difference with dplyr::summarize() is that summarize() only accepts grouped data). It will contain one column for each grouping variable and one column for each of the summary statistics that you have specified.

Usage

## S3 method for class 'RPolarsDataFrame'
summarize(.data, ..., .by = NULL, .groups = "drop_last")

## S3 method for class 'RPolarsDataFrame'
summarise(.data, ..., .by = NULL, .groups = "drop_last")

## S3 method for class 'RPolarsLazyFrame'
summarize(.data, ..., .by = NULL, .groups = "drop_last")

## S3 method for class 'RPolarsLazyFrame'
summarise(.data, ..., .by = NULL, .groups = "drop_last")

Arguments

.data

A Polars Data/LazyFrame
...

Name-value pairs. The name gives the name of the column in the output. The value can be:

  • A vector the same length as the current group (or the whole data frame if ungrouped).

  • NULL, to remove the column.

across() is mostly supported, except in a few cases. In particular, if the .cols argument is where(...), it will not select variables that were created before across(). Other select helpers are supported. See the examples.
.by

Optionally, a selection of columns to group by for just this operation, functioning as an alternative to group_by(). The group order is not maintained, use group_by() if you want more control over it.
.groups

Grouping structure of the result. Must be one of:

  • "drop_last" (default): drop the last level of grouping;

  • "drop": all levels of grouping are dropped;

  • "keep": keep the same grouping structure as .data.

For now, "rowwise" is not supported. Note that dplyr uses .groups = NULL by default, whose behavior depends on the number of rows by group in the output. However, returning several rows by group in summarize() is deprecated (one should use reframe() instead), which is why .groups = NULL is not supported by tidypolars.

Examples

mtcars |>
  as_polars_df() |>
  group_by(cyl) |>
  summarize(m_gear = mean(gear), sd_gear = sd(gear))

# an alternative syntax is to use `.by`
mtcars |>
  as_polars_df() |>
  summarize(m_gear = mean(gear), sd_gear = sd(gear), .by = cyl)

Summary statistics for a Polars DataFrame

Description

Summary statistics for a Polars DataFrame

Usage

## S3 method for class 'RPolarsDataFrame'
summary(object, percentiles = c(0.25, 0.75), ...)

Arguments

object

A Polars DataFrame.
percentiles

One or more percentiles to include in the summary statistics. All values must be between 0 and 1 (NULL are ignored).
...

Ignored.

Examples

mtcars |>
  as_polars_df() |>
  summary(percentiles = c(0.2, 0.4, 0.6, 0.8))

tidypolars global options

Description

There is currently one global option:

  • tidypolars_unknown_args controls what happens when some arguments passed in an expression are unknown, e.g the argument prob in sample(). The default ("warn") only warns the user that some arguments are ignored by tidypolars. The only other accepted value is "error" to throw an error when this happens.

Examples

options(tidypolars_unknown_args = "warn")
test <- polars::pl$DataFrame(x = c(2, 1, 5, 3, 1))

# The default is to warn the user
mutate(test, x2 = sample(x, prob = 0.5))

# But one can make this stricter and throw an error when this happens
options(tidypolars_unknown_args = "error")
try(mutate(test, x2 = sample(x, prob = 0.5)))

options(tidypolars_unknown_args = "warn")

Uncount a Data/LazyFrame

Description

This duplicates rows according to a weighting variable (or expression). This is the opposite of count().

Usage

## S3 method for class 'RPolarsDataFrame'
uncount(data, weights, ..., .remove = TRUE, .id = NULL)

## S3 method for class 'RPolarsLazyFrame'
uncount(data, weights, ..., .remove = TRUE, .id = NULL)

Arguments

data

A Polars Data/LazyFrame
weights

A vector of weights. Evaluated in the context of data.
...

Not used.
.remove

If TRUE, and weights is the name of a column in data, then this column is removed.
.id

Supply a string to create a new variable which gives a unique identifier for each created row.

Examples

test <- polars::pl$DataFrame(x = c("a", "b"), y = 100:101, n = c(1, 2))
test

uncount(test, n)

uncount(test, n, .id = "id")

# using constants
uncount(test, 2)

# using expressions
uncount(test, 2 / n)

Unite multiple columns into one by pasting strings together

Description

Unite multiple columns into one by pasting strings together

Usage

## S3 method for class 'RPolarsDataFrame'
unite(data, col, ..., sep = "_", remove = TRUE, na.rm = FALSE)

## S3 method for class 'RPolarsLazyFrame'
unite(data, col, ..., sep = "_", remove = TRUE, na.rm = FALSE)

Arguments

data

A Polars Data/LazyFrame
col

The name of the new column, as a string or symbol.
...

Any expression accepted by dplyr::select(): variable names, column numbers, select helpers, etc.
sep

Separator to use between values.
remove

If TRUE, remove input columns from the output Data/LazyFrame.
na.rm

If TRUE, missing values will be replaced with an empty string prior to uniting each value.

Examples

test <- polars::pl$DataFrame(
  year = 2009:2011,
  month = 10:12,
  day = c(11L, 22L, 28L),
  name_day = c("Monday", "Thursday", "Wednesday")
)

# By default, united columns are dropped
unite(test, col = "full_date", year, month, day, sep = "-")
unite(test, col = "full_date", year, month, day, sep = "-", remove = FALSE)

test2 <- polars::pl$DataFrame(
  name = c("John", "Jack", "Thomas"),
  middlename = c("T.", NA, "F."),
  surname = c("Smith", "Thompson", "Jones")
)

# By default, NA values are kept in the character output
unite(test2, col = "full_name", everything(), sep = " ")
unite(test2, col = "full_name", everything(), sep = " ", na.rm = TRUE)

Export data to CSV file(s)

Description

Export data to CSV file(s)

Usage

write_csv_polars(
  .data,
  file,
  ...,
  include_bom = FALSE,
  include_header = TRUE,
  separator = ",",
  line_terminator = "\n",
  quote = "\"",
  batch_size = 1024,
  datetime_format = NULL,
  date_format = NULL,
  time_format = NULL,
  float_precision = NULL,
  null_values = "",
  quote_style = "necessary"
)

Arguments

.data

A Polars DataFrame.
file

File path to which the result should be written.
...

Ignored.
include_bom

Whether to include UTF-8 BOM (byte order mark) in the CSV output.
include_header

Whether to include header in the CSV output.
separator

Separate CSV fields with this symbol.
line_terminator

String used to end each row.
quote

Byte to use as quoting character.
batch_size

Number of rows that will be processed per thread.
datetime_format

A format string, with the specifiers defined by the chrono Rust crate. If no format specified, the default fractional-second precision is inferred from the maximum timeunit found in the frame’s Datetime cols (if any).
date_format

A format string, with the specifiers defined by the chrono Rust crate.
time_format

A format string, with the specifiers defined by the chrono Rust crate.
float_precision

Number of decimal places to write, applied to both Float32 and Float64 datatypes.
null_values

A string representing null values (defaulting to the empty string).
quote_style

Determines the quoting strategy used.

  • "necessary" (default): This puts quotes around fields only when necessary. They are necessary when fields contain a quote, delimiter or record terminator. Quotes are also necessary when writing an empty record (which is indistinguishable from a record with one empty field). This is the default.

  • "always": This puts quotes around every field.

  • "non_numeric": This puts quotes around all fields that are non-numeric. Namely, when writing a field that does not parse as a valid float or integer, then quotes will be used even if they aren't strictly necessary.

  • "never": This never puts quotes around fields, even if that results in invalid CSV data (e.g. by not quoting strings containing the separator).

Value

The input DataFrame.

Examples

dest <- tempfile(fileext = ".csv")
mtcars |>
  as_polars_df() |>
  write_csv_polars(dest)

read.csv(dest)

Export data to IPC file(s)

Description

Export data to IPC file(s)

Usage

write_ipc_polars(
  .data,
  file,
  compression = "uncompressed",
  ...,
  future = FALSE
)

Arguments

.data

A Polars DataFrame.
file

File path to which the result should be written.
compression

NULL or a character of the compression method, "uncompressed" or "lz4" or "zstd". NULL is equivalent to "uncompressed". Choose "zstd" for good compression performance. Choose "lz4" for fast compression/decompression.
...

Ignored.
future

Setting this to TRUE will write Polars' internal data structures that might not be available by other Arrow implementations.

Value

The input DataFrame.

Export data to JSON file(s)

Description

Export data to JSON file(s)

Usage

write_json_polars(.data, file, ..., pretty = FALSE, row_oriented = FALSE)

Arguments

.data

A Polars DataFrame.
file

File path to which the result should be written.
...

Ignored.
pretty

Pretty serialize JSON.
row_oriented

Write to row-oriented JSON. This is slower, but more common.

Value

The input DataFrame.

Examples

dest <- tempfile(fileext = ".json")
mtcars |>
  as_polars_df() |>
  write_json_polars(dest)

jsonlite::fromJSON(dest)

Export data to NDJSON file(s)

Description

Export data to NDJSON file(s)

Usage

write_ndjson_polars(.data, file)

Arguments

.data

A Polars DataFrame.
file

File path to which the result should be written.

Value

The input DataFrame.

Examples

dest <- tempfile(fileext = ".ndjson")
mtcars |>
  as_polars_df() |>
  write_ndjson_polars(dest)

jsonlite::stream_in(file(dest), verbose = FALSE)

Export data to Parquet file(s)

Description

Export data to Parquet file(s)

Usage

write_parquet_polars(
  .data,
  file,
  ...,
  compression = "zstd",
  compression_level = 3,
  statistics = TRUE,
  row_group_size = NULL,
  data_page_size = NULL,
  partition_by = NULL,
  partition_chunk_size_bytes = 4294967296
)

Arguments

.data

A Polars DataFrame.
file

File path to which the result should be written.
...

Ignored.
compression

The compression method. One of :

  • "uncompressed"

  • "zstd" (default): good compression performance

  • "lz4": fast compression / decompression

  • "snappy": more backwards compatibility guarantees when you deal with older parquet readers.

  • "gzip", "lzo", "brotli"

compression_level

The level of compression to use (default is 3). Only used if compression is one of "gzip", "brotli", or "zstd". Higher compression means smaller files on disk.

  • "gzip" : min-level = 0, max-level = 10

  • "brotli" : min-level = 0, max-level = 11

  • "zstd" : min-level = 1, max-level = 22.

statistics

Whether to compute and write column statistics (default is FALSE). This requires more computations.
row_group_size

Size of the row groups in number of rows. If NULL (default), the chunks of the DataFrame are used. Writing in smaller chunks may reduce memory pressure and improve writing speeds.
data_page_size

If NULL (default), the limit will be around 1MB.
partition_by

Column(s) to partition by. A partitioned dataset will be written if this is specified.
partition_chunk_size_bytes

Approximate size to split DataFrames within a single partition when writing. Note this is calculated using the size of the DataFrame in memory - the size of the output file may differ depending on the file format / compression.

Value

The input DataFrame.

Examples

dest <- tempfile(fileext = ".parquet")
mtcars |>
  as_polars_df() |>
  write_parquet_polars(dest)

nanoparquet::read_parquet(dest)