Implement add_rownames()

Closes tidyverse#639

NAMESPACE

@@ -289,6 +289,7 @@ S3method(update,tbl_sql)
 export("%.%")
 export("%>%")
 export(.datatable.aware)
+export(add_rownames)
 export(anti_join)
 export(arrange)
 export(arrange_)

R/dataframe.R

@@ -130,3 +130,22 @@ as_data_frame <- function(x) {
 
   x
 }
+
+#' Convert row names to an explicit variable.
+#'
+#' @param df Input data frame with rownames.
+#' @param var Name of variable to use
+#' @export
+#' @examples
+#' mtcars %>%
+#'   tbl_df() %>%
+#'   print() %>%
+#'   add_rownames()
+add_rownames <- function(df, var = "rowname") {
+  stopifnot(is.data.frame(df))
+
+  df[[var]] <- rownames(df)
+  rownames(df) <- NULL
+
+  df
+}

man/add_rownames.Rd

@@ -0,0 +1,22 @@
+% Generated by roxygen2 (4.0.2): do not edit by hand
+\name{add_rownames}
+\alias{add_rownames}
+\title{Convert row names to an explicit variable.}
+\usage{
+add_rownames(df, var = "rowname")
+}
+\arguments{
+\item{df}{Input data frame with rownames.}
+
+\item{var}{Name of variable to use}
+}
+\description{
+Convert row names to an explicit variable.
+}
+\examples{
+mtcars \%>\%
+  tbl_df() \%>\%
+  print() \%>\%
+  add_rownames()
+}
+