polars select for lazyframe
Selects columns from lazyframe.
Signature
> polars select {flags} ...rest
Parameters
-
...rest: Expression(s) that define the column selection.
Input/output types:
| input | output |
|---|---|
| polars_dataframe | polars_dataframe |
| polars_lazyframe | polars_lazyframe |
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 │ ╰───┴───╯
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https://www.nushell.sh/commands/docs/polars_select.html
