polars group-by for lazyframe
Creates a group-by object that can be used for other aggregations.
Signature
> polars group-by {flags} ...rest
Flags
-
--maintain-order, -m: Ensure that the order of the groups is consistent with the input data. This is slower than a default group by and cannot be run on the streaming engine.
Parameters
-
...rest: Expression(s) that define the lazy group-by.
Input/output types:
| input | output |
|---|---|
| polars_dataframe | polars_dataframe |
| polars_lazyframe | polars_lazyframe |
Examples
Group by and perform an aggregation
> [[a b]; [1 2] [1 4] [2 6] [2 4]]
| polars into-lazy
| polars group-by a
| polars agg [
(polars col b | polars min | polars as "b_min")
(polars col b | polars max | polars as "b_max")
(polars col b | polars sum | polars as "b_sum")
]
| polars collect
| polars sort-by a
╭───┬───┬───────┬───────┬───────╮
│ # │ a │ b_min │ b_max │ b_sum │
├───┼───┼───────┼───────┼───────┤
│ 0 │ 1 │ 2 │ 4 │ 6 │
│ 1 │ 2 │ 4 │ 6 │ 10 │
╰───┴───┴───────┴───────┴───────╯
Group by an expression and perform an aggregation
> [[a b]; [2025-04-01 1] [2025-04-02 2] [2025-04-03 3] [2025-04-04 4]]
| polars into-lazy
| polars group-by (polars col a | polars get-day | $in mod 2)
| polars agg [
(polars col b | polars min | polars as "b_min")
(polars col b | polars max | polars as "b_max")
(polars col b | polars sum | polars as "b_sum")
]
| polars collect
| polars sort-by a
╭───┬───┬───────┬───────┬───────╮
│ # │ a │ b_min │ b_max │ b_sum │
├───┼───┼───────┼───────┼───────┤
│ 0 │ 0 │ 2 │ 4 │ 6 │
│ 1 │ 1 │ 1 │ 3 │ 4 │
╰───┴───┴───────┴───────┴───────╯
Copyright © 2019–2026 The Nushell Project DevelopersLicensed under the MIT License.
https://www.nushell.sh/commands/docs/polars_group-by.html
