polars first for dataframe
Show only the first number of rows or create a first expression
Signature
> polars first {flags} (rows)
Parameters
-
rows: Starting from the front, the number of rows to return.
Input/output types:
| input | output |
|---|---|
| polars_expression | polars_expression |
| polars_dataframe | polars_dataframe |
| polars_lazyframe | polars_lazyframe |
Examples
Return the first row of a dataframe
> [[a b]; [1 2] [3 4]] | polars into-df | polars first ╭───┬───┬───╮ │ # │ a │ b │ ├───┼───┼───┤ │ 0 │ 1 │ 2 │ ╰───┴───┴───╯
Return the first two rows of a dataframe
> [[a b]; [1 2] [3 4]] | polars into-df | polars first 2 ╭───┬───┬───╮ │ # │ a │ b │ ├───┼───┼───┤ │ 0 │ 1 │ 2 │ │ 1 │ 3 │ 4 │ ╰───┴───┴───╯
Creates a first expression from a column
> polars col a | polars first
Aggregate the first values in the group.
> [[a b c d]; [1 0.5 true Apple] [2 0.5 true Orange] [2 4 true Apple] [3 10 false Apple] [4 13 false Banana] [5 14 true Banana]] | polars into-df -s {a: u8, b: f32, c: bool, d: str} | polars group-by d | polars first | polars sort-by [a] | polars collect
╭───┬────────┬───┬───────┬───────╮
│ # │ d │ a │ b │ c │
├───┼────────┼───┼───────┼───────┤
│ 0 │ Apple │ 1 │ 0.50 │ true │
│ 1 │ Orange │ 2 │ 0.50 │ true │
│ 2 │ Banana │ 4 │ 13.00 │ false │
╰───┴────────┴───┴───────┴───────╯
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https://www.nushell.sh/commands/docs/polars_first.html
