polars select

For lazyframe.

warning This command requires a plugin The polars select command resides in the polars plugin. To use this command, you must install and register nu_plugin_polars. See the Plugins chapter in the book for more information.

Command Type

plugin

Signature

> polars select {flags} ...rest

Parameters

• ...rest: Expression(s) that define the column selection.

Input/output types:

Examples

Select a column from the dataframe

> [[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select a
╭───┬───╮
│ # │ a │
├───┼───┤
│ 0 │ 6 │
│ 1 │ 4 │
│ 2 │ 2 │
╰───┴───╯

Select a column from a dataframe using a record

> [[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select {c: ((polars col a) * 2)}
╭───┬────╮
│ # │ c  │
├───┼────┤
│ 0 │ 12 │
│ 1 │  8 │
│ 2 │  4 │
╰───┴────╯

Select a column from a dataframe using a mix of expressions and record of expressions

> [[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select a b {c: ((polars col a) ** 2)}
╭───┬───┬───┬────╮
│ # │ a │ b │ c  │
├───┼───┼───┼────┤
│ 0 │ 6 │ 2 │ 36 │
│ 1 │ 4 │ 2 │ 16 │
│ 2 │ 2 │ 2 │  4 │
╰───┴───┴───┴────╯

Select all columns from a dataframe using a selector

> [[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars select (polars selector all)
╭───┬───┬───╮
│ # │ a │ b │
├───┼───┼───┤
│ 0 │ 6 │ 2 │
│ 1 │ 4 │ 2 │
│ 2 │ 2 │ 2 │
╰───┴───┴───╯

Select columns by name using a selector

> [[a b c]; [1 2 3] [4 5 6]] | polars into-df | polars select (polars selector by-name a c)
╭───┬───┬───╮
│ # │ a │ c │
├───┼───┼───┤
│ 0 │ 1 │ 3 │
│ 1 │ 4 │ 6 │
╰───┴───┴───╯

Select the first column using a selector

> [[a b c]; [1 2 3] [4 5 6]] | polars into-df | polars select (polars selector first)
╭───┬───╮
│ # │ a │
├───┼───┤
│ 0 │ 1 │
│ 1 │ 4 │
╰───┴───╯

Ported from nushell/nushell.github.io. Copyright (c) 2021 Nushell Project. MIT License.