feat: add missing functions and docs for selectors

NAMESPACE

@@ -91,6 +91,7 @@ S3method(as_polars_series,vctrs_unspecified)
 S3method(dim,polars_data_frame)
 S3method(length,polars_data_frame)
 S3method(length,polars_series)
+S3method(names,polars_data_frame)
 S3method(parse_as_polars_duration_string,"NULL")
 S3method(parse_as_polars_duration_string,character)
 S3method(parse_as_polars_duration_string,clock_duration)

R/000-wrappers.R

@@ -124,6 +124,21 @@ NULL
 }
 
 
+`index_cols` <- function(`indices`) {
+  .savvy_wrap_PlRExpr(.Call(savvy_index_cols__impl, `indices`))
+}
+
+
+`first` <- function() {
+  .savvy_wrap_PlRExpr(.Call(savvy_first__impl))
+}
+
+
+`last` <- function() {
+  .savvy_wrap_PlRExpr(.Call(savvy_last__impl))
+}
+
+
 `lit_from_bool` <- function(`value`) {
   .savvy_wrap_PlRExpr(.Call(savvy_lit_from_bool__impl, `value`))
 }

R/dataframe-s3-base.R

@@ -10,6 +10,9 @@ dim.polars_data_frame <- function(x) x$shape
 #' @export
 length.polars_data_frame <- function(x) x$width
 
+#' @export
+names.polars_data_frame <- function(x) x$columns
+
 #' Export the polars object as an R list
 #'
 #' This S3 method calls [`as_polars_df(x, ...)$get_columns()`][dataframe__get_columns] or

R/functions-col.R

@@ -64,3 +64,60 @@ pl__col <- function(...) {
     }
   })
 }
+
+#' Get the nth column(s) of the context
+#'
+#' @param indices One or more indices representing the columns to retrieve.
+#'
+#' @inherit as_polars_expr return
+#' @examples
+#' df <- pl$DataFrame(
+#'   a = c(1, 8, 3),
+#'   b = c(4, 5, 2),
+#'   c = c("foo", "bar", "baz")
+#' )
+#'
+#' df$select(pl$nth(1))
+#' df$select(pl$nth(c(2, 0)))
+pl__nth <- function(indices) {
+  wrap({
+    if (is.numeric(indices) && anyNA(indices)) {
+      abort("`indices` must not contain any NA values.")
+    }
+    index_cols(indices)
+  })
+}
+
+#' Get the first column of the context
+#'
+#' @inherit as_polars_expr return
+#' @examples
+#' df <- pl$DataFrame(
+#'   a = c(1, 8, 3),
+#'   b = c(4, 5, 2),
+#'   c = c("foo", "bar", "baz")
+#' )
+#'
+#' df$select(pl$first())
+pl__first <- function() {
+  wrap({
+    first()
+  })
+}
+
+#' Get the last column of the context
+#'
+#' @inherit as_polars_expr return
+#' @examples
+#' df <- pl$DataFrame(
+#'   a = c(1, 8, 3),
+#'   b = c(4, 5, 2),
+#'   c = c("foo", "bar", "baz")
+#' )
+#'
+#' df$select(pl$last())
+pl__last <- function() {
+  wrap({
+    last()
+  })
+}