Return the row indices that would sort the columns

Source code

Description

Return the row indices that would sort the columns

Usage

pl$arg_sort_by(
  ...,
  descending = FALSE,
  nulls_last = FALSE,
  multithreaded = TRUE,
  maintain_order = FALSE
)

Arguments

…	Column(s) to arg sort by. Can be Expr(s) or something coercible to Expr(s). Strings are parsed as column names.
descending	A logical. If TRUE, sort in descending order.
nulls_last	A logical. If TRUE, place null values last insead of first.
multithreaded	A logical. If TRUE, sort using multiple threads.
maintain_order	Whether the order should be maintained if elements are equal. If TRUE, streaming is not possible and performance might be worse since this requires a stable search.

Value

Expr

See Also

$arg_sort() to find the row indices that would sort an Expr.

Examples

library(polars)

df = pl$DataFrame(
  a = c(0, 1, 1, 0),
  b = c(3, 2, 3, 2)
)

df$with_columns(
  arg_sort_a = pl$arg_sort_by("a"),
  arg_sort_ab = pl$arg_sort_by(c("a", "b"), descending = TRUE)
)

#> shape: (4, 4)
#> ┌─────┬─────┬────────────┬─────────────┐
#> │ a   ┆ b   ┆ arg_sort_a ┆ arg_sort_ab │
#> │ --- ┆ --- ┆ ---        ┆ ---         │
#> │ f64 ┆ f64 ┆ u32        ┆ u32         │
#> ╞═════╪═════╪════════════╪═════════════╡
#> │ 0.0 ┆ 3.0 ┆ 0          ┆ 2           │
#> │ 1.0 ┆ 2.0 ┆ 3          ┆ 1           │
#> │ 1.0 ┆ 3.0 ┆ 1          ┆ 0           │
#> │ 0.0 ┆ 2.0 ┆ 2          ┆ 3           │
#> └─────┴─────┴────────────┴─────────────┘

# we can also pass Expr
df$with_columns(
  arg_sort_a = pl$arg_sort_by(pl$col("a") * -1)
)

#> shape: (4, 3)
#> ┌─────┬─────┬────────────┐
#> │ a   ┆ b   ┆ arg_sort_a │
#> │ --- ┆ --- ┆ ---        │
#> │ f64 ┆ f64 ┆ u32        │
#> ╞═════╪═════╪════════════╡
#> │ 0.0 ┆ 3.0 ┆ 1          │
#> │ 1.0 ┆ 2.0 ┆ 2          │
#> │ 1.0 ┆ 3.0 ┆ 0          │
#> │ 0.0 ┆ 2.0 ┆ 3          │
#> └─────┴─────┴────────────┘