polars col
for expression
Creates a named column expression.
This command requires a plugin
The polars col
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.
Signature
> polars col {flags} (column name) ...rest
Flags
--type, -t
: Treat column names as type names
Parameters
column name
: Name of column to be used. '*' can be used for all columns....rest
: Additional columns to be used. Cannot be '*'
Input/output types:
input | output |
---|---|
any | any |
Examples
Creates a named column expression and converts it to a nu object
> polars col a | polars into-nu
╭───────┬────────╮
│ expr │ column │
│ value │ a │
╰───────┴────────╯
Select all columns using the asterisk wildcard.
> [[a b]; [x 1] [y 2] [z 3]] | polars into-df | polars select (polars col '*') | polars collect
╭───┬───┬───╮
│ # │ a │ b │
├───┼───┼───┤
│ 0 │ x │ 1 │
│ 1 │ y │ 2 │
│ 2 │ z │ 3 │
╰───┴───┴───╯
Select multiple columns (cannot be used with asterisk wildcard)
> [[a b c]; [x 1 1.1] [y 2 2.2] [z 3 3.3]] | polars into-df | polars select (polars col b c | polars sum) | polars collect
╭───┬───┬──────╮
│ # │ b │ c │
├───┼───┼──────┤
│ 0 │ 6 │ 6.60 │
╰───┴───┴──────╯
Select multiple columns by types (cannot be used with asterisk wildcard)
> [[a b c]; [x o 1.1] [y p 2.2] [z q 3.3]] | polars into-df | polars select (polars col str f64 --type | polars max) | polars collect
╭───┬───┬───┬──────╮
│ # │ a │ b │ c │
├───┼───┼───┼──────┤
│ 0 │ z │ q │ 3.30 │
╰───┴───┴───┴──────╯