Get maximum value, ordered by another expression

Source code

Description

Usage

<Expr>$max_by(by)

Arguments

by	Column used to determine the largest element. Accepts expression input. Strings are parsed as column names.

Value

A polars expression

Examples

library("polars")

df <- pl$DataFrame(a = c(-1, NaN, 1), b = c("x", "y", "z"))
df$with_columns(max_b_by_a = pl$col("b")$max_by("a"))

#> shape: (3, 3)
#> ┌──────┬─────┬────────────┐
#> │ a    ┆ b   ┆ max_b_by_a │
#> │ ---  ┆ --- ┆ ---        │
#> │ f64  ┆ str ┆ str        │
#> ╞══════╪═════╪════════════╡
#> │ -1.0 ┆ x   ┆ z          │
#> │ NaN  ┆ y   ┆ z          │
#> │ 1.0  ┆ z   ┆ z          │
#> └──────┴─────┴────────────┘