Get the column name that this expression would produce

Description

It may not always be possible to determine the output name as that can depend on the schema of the context; in that case this will raise an error if raise_if_undetermined is TRUE (the default), or return NA otherwise.

Usage

<Expr>$meta$output_name(..., raise_if_undetermined = TRUE)

Arguments

`…`	Ignored.
`raise_if_undetermined`	If `TRUE` (default), raise an error if the output name cannot be determined. Otherwise, return `NA`.

Value

A character vector

Examples

library("polars")

e = pl$col("foo") * pl$col("bar")
e$meta$output_name()

#> [1] "foo"

e_filter = pl$col("foo")$filter(pl$col("bar") == 13)
e_filter$meta$output_name()

#> [1] "foo"

e_sum_over = pl$sum("foo")$over("groups")
e_sum_over$meta$output_name()

#> [1] "foo"

e_sum_slice = pl$sum("foo")$slice(pl$len() - 10, pl$col("bar"))
e_sum_slice$meta$output_name()

#> [1] "foo"

pl$len()$meta$output_name()

#> [1] "len"

pl$col("*")$meta$output_name(raise_if_undetermined = FALSE)

#> [1] NA