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Alias for an element being evaluated in an eval expression

Description

Alias for an element being evaluated in an eval expression

Usage

pl$element()

Value

A polars expression

Examples

library("polars")

# A horizontal rank computation by taking the elements of a list:
df <- pl$DataFrame(
  a = c(1, 8, 3),
  b = c(4, 5, 2)
)
df$with_columns(
  rank = pl$concat_list(c("a", "b"))$list$eval(pl$element()$rank())
)

#> shape: (3, 3)
#> ┌─────┬─────┬────────────┐
#> │ a   ┆ b   ┆ rank       │
#> │ --- ┆ --- ┆ ---        │
#> │ f64 ┆ f64 ┆ list[f64]  │
#> ╞═════╪═════╪════════════╡
#> │ 1.0 ┆ 4.0 ┆ [1.0, 2.0] │
#> │ 8.0 ┆ 5.0 ┆ [2.0, 1.0] │
#> │ 3.0 ┆ 2.0 ┆ [2.0, 1.0] │
#> └─────┴─────┴────────────┘

# A mathematical operation on array elements:
df <- pl$DataFrame(
  a = c(1, 8, 3),
  b = c(4, 5, 2)
)
df$with_columns(
  a_b_doubled = pl$concat_list(c("a", "b"))$list$eval(pl$element() * 2)
)

#> shape: (3, 3)
#> ┌─────┬─────┬──────────────┐
#> │ a   ┆ b   ┆ a_b_doubled  │
#> │ --- ┆ --- ┆ ---          │
#> │ f64 ┆ f64 ┆ list[f64]    │
#> ╞═════╪═════╪══════════════╡
#> │ 1.0 ┆ 4.0 ┆ [2.0, 8.0]   │
#> │ 8.0 ┆ 5.0 ┆ [16.0, 10.0] │
#> │ 3.0 ┆ 2.0 ┆ [6.0, 4.0]   │
#> └─────┴─────┴──────────────┘