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Group by one or more variables

Source: R/groups.R
group_by.RPolarsDataFrame.Rd

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
#> shape: (32, 11)
#> ┌──────┬─────┬───────┬───────┬───┬─────┬─────┬──────┬──────┐
#> │ mpg  ┆ cyl ┆ disp  ┆ hp    ┆ … ┆ vs  ┆ am  ┆ gear ┆ carb │
#> │ ---  ┆ --- ┆ ---   ┆ ---   ┆   ┆ --- ┆ --- ┆ ---  ┆ ---  │
#> │ f64  ┆ f64 ┆ f64   ┆ f64   ┆   ┆ f64 ┆ f64 ┆ f64  ┆ f64  │
#> ╞══════╪═════╪═══════╪═══════╪═══╪═════╪═════╪══════╪══════╡
#> │ 21.0 ┆ 6.0 ┆ 160.0 ┆ 110.0 ┆ … ┆ 0.0 ┆ 1.0 ┆ 4.0  ┆ 4.0  │
#> │ 21.0 ┆ 6.0 ┆ 160.0 ┆ 110.0 ┆ … ┆ 0.0 ┆ 1.0 ┆ 4.0  ┆ 4.0  │
#> │ 22.8 ┆ 4.0 ┆ 108.0 ┆ 93.0  ┆ … ┆ 1.0 ┆ 1.0 ┆ 4.0  ┆ 1.0  │
#> │ 21.4 ┆ 6.0 ┆ 258.0 ┆ 110.0 ┆ … ┆ 1.0 ┆ 0.0 ┆ 3.0  ┆ 1.0  │
#> │ 18.7 ┆ 8.0 ┆ 360.0 ┆ 175.0 ┆ … ┆ 0.0 ┆ 0.0 ┆ 3.0  ┆ 2.0  │
#> │ …    ┆ …   ┆ …     ┆ …     ┆ … ┆ …   ┆ …   ┆ …    ┆ …    │
#> │ 30.4 ┆ 4.0 ┆ 95.1  ┆ 113.0 ┆ … ┆ 1.0 ┆ 1.0 ┆ 5.0  ┆ 2.0  │
#> │ 15.8 ┆ 8.0 ┆ 351.0 ┆ 264.0 ┆ … ┆ 0.0 ┆ 1.0 ┆ 5.0  ┆ 4.0  │
#> │ 19.7 ┆ 6.0 ┆ 145.0 ┆ 175.0 ┆ … ┆ 0.0 ┆ 1.0 ┆ 5.0  ┆ 6.0  │
#> │ 15.0 ┆ 8.0 ┆ 301.0 ┆ 335.0 ┆ … ┆ 0.0 ┆ 1.0 ┆ 5.0  ┆ 8.0  │
#> │ 21.4 ┆ 4.0 ┆ 121.0 ┆ 109.0 ┆ … ┆ 1.0 ┆ 1.0 ┆ 4.0  ┆ 2.0  │
#> └──────┴─────┴───────┴───────┴───┴─────┴─────┴──────┴──────┘
#> Groups [3]: cyl
#> Maintain order: FALSE

by_cyl |> summarise(
  disp = mean(disp),
  hp = mean(hp)
)
#> shape: (3, 3)
#> ┌─────┬────────────┬────────────┐
#> │ cyl ┆ disp       ┆ hp         │
#> │ --- ┆ ---        ┆ ---        │
#> │ f64 ┆ f64        ┆ f64        │
#> ╞═════╪════════════╪════════════╡
#> │ 6.0 ┆ 183.314286 ┆ 122.285714 │
#> │ 4.0 ┆ 105.136364 ┆ 82.636364  │
#> │ 8.0 ┆ 353.1      ┆ 209.214286 │
#> └─────┴────────────┴────────────┘
by_cyl |> filter(disp == max(disp))
#> shape: (3, 11)
#> ┌──────┬─────┬───────┬───────┬───┬─────┬─────┬──────┬──────┐
#> │ mpg  ┆ cyl ┆ disp  ┆ hp    ┆ … ┆ vs  ┆ am  ┆ gear ┆ carb │
#> │ ---  ┆ --- ┆ ---   ┆ ---   ┆   ┆ --- ┆ --- ┆ ---  ┆ ---  │
#> │ f64  ┆ f64 ┆ f64   ┆ f64   ┆   ┆ f64 ┆ f64 ┆ f64  ┆ f64  │
#> ╞══════╪═════╪═══════╪═══════╪═══╪═════╪═════╪══════╪══════╡
#> │ 21.4 ┆ 6.0 ┆ 258.0 ┆ 110.0 ┆ … ┆ 1.0 ┆ 0.0 ┆ 3.0  ┆ 1.0  │
#> │ 24.4 ┆ 4.0 ┆ 146.7 ┆ 62.0  ┆ … ┆ 1.0 ┆ 0.0 ┆ 4.0  ┆ 2.0  │
#> │ 10.4 ┆ 8.0 ┆ 472.0 ┆ 205.0 ┆ … ┆ 0.0 ┆ 0.0 ┆ 3.0  ┆ 4.0  │
#> └──────┴─────┴───────┴───────┴───┴─────┴─────┴──────┴──────┘
#> Groups [3]: cyl
#> Maintain order: FALSE