Select and modify columns of a DataFrame

Description

Select and perform operations on a subset of columns only. This discards unmentioned columns (like .() in data.table and contrarily to dplyr::mutate()).

One cannot use new variables in subsequent expressions in the same $select() call. For instance, if you create a variable x, you will only be able to use it in another $select() or $with_columns() call.

Usage

<DataFrame>$select(...)

Arguments

…	\<dynamic-dots\> Name-value pairs of objects to be converted to polars expressions by the as_polars_expr() function. Characters are parsed as column names, other non-expression inputs are parsed as literals. Each name will be used as the expression name.

Value

A polars DataFrame

Examples

library("polars")

as_polars_df(iris)$select(
  abs_SL = pl$col("Sepal.Length")$abs(),
  add_2_SL = pl$col("Sepal.Length") + 2
)

#> shape: (150, 2)
#> ┌────────┬──────────┐
#> │ abs_SL ┆ add_2_SL │
#> │ ---    ┆ ---      │
#> │ f64    ┆ f64      │
#> ╞════════╪══════════╡
#> │ 5.1    ┆ 7.1      │
#> │ 4.9    ┆ 6.9      │
#> │ 4.7    ┆ 6.7      │
#> │ 4.6    ┆ 6.6      │
#> │ 5.0    ┆ 7.0      │
#> │ …      ┆ …        │
#> │ 6.7    ┆ 8.7      │
#> │ 6.3    ┆ 8.3      │
#> │ 6.5    ┆ 8.5      │
#> │ 6.2    ┆ 8.2      │
#> │ 5.9    ┆ 7.9      │
#> └────────┴──────────┘