Operations on Polars grouped DataFrame
Description
The GroupBy class in R, is just another interface on top of the
DataFrame in rust polars. Groupby does not use the rust api for
\<DataFrame>$group_by()
+ $agg()
because the
groupby-struct is a reference to a DataFrame and that reference will
share lifetime with its parent DataFrame.
Details
There is no way to expose lifetime limited objects via extendr currently
(might be quirky anyhow with R GC). Instead the inputs for the
group_by
are just stored on R side, until also
agg
is called. Which will end up in a self-owned DataFrame
object and all is fine. groupby aggs are performed via the rust polars
LazyGroupBy methods, see DataFrame.groupby_agg method.
Active bindings
columns
$columns
returns a character
vector with the column names.
Examples
#> shape: (3, 2)
#> ┌─────┬───────┐
#> │ cyl ┆ mpg │
#> │ --- ┆ --- │
#> │ f64 ┆ f64 │
#> ╞═════╪═══════╡
#> │ 4.0 ┆ 293.3 │
#> │ 8.0 ┆ 211.4 │
#> │ 6.0 ┆ 138.2 │
#> └─────┴───────┘