Merge pull request #74 from hadley/feature/31-dub

- New `enframe()` that converts vectors to two-column tibbles (#31, #74).

NAMESPACE

@@ -37,6 +37,7 @@ export(as_data_frame)
 export(column_to_rownames)
 export(data_frame)
 export(data_frame_)
+export(enframe)
 export(frame_data)
 export(glimpse)
 export(has_rownames)

R/enframe.R

@@ -0,0 +1,24 @@
+#' Converting atomic vectors to data frames
+#'
+#' A helper function that converts named atomic vectors or lists to two-column
+#' data frames.
+#' For unnamed vectors, the natural sequence is used as name column.
+#'
+#' @param x An atomic vector
+#' @param name,value Names of the columns that store the names and values
+#'
+#' @return A \code{\link{data_frame}}
+#' @export
+#'
+#' @examples
+#' enframe(1:3)
+#' enframe(c(a = 5, b = 7))
+enframe <- function(x, name = "name", value = "value") {
+  if (is.null(names(x))) {
+    df <- data_frame(seq_along(x), x)
+  } else {
+    df <- data_frame(names(x), unname(x))
+  }
+  names(df) <- c(name, value)
+  df
+}

tests/testthat/test-enframe.R

@@ -0,0 +1,22 @@
+context("enframe")
+
+test_that("can convert unnamed vector", {
+  expect_identical(enframe(3:1),
+                   data_frame(name = 1:3, value = 3:1))
+})
+
+test_that("can convert named vector", {
+  expect_identical(enframe(c(a = 2, b = 1)),
+                   data_frame(name = letters[1:2], value = as.numeric(2:1)))
+})
+
+test_that("can convert zero-length vector", {
+  expect_identical(enframe(logical()),
+                   data_frame(name = integer(), value = logical()))
+})
+
+test_that("can use custom names", {
+  expect_identical(enframe(letters, name = "index", value = "letter"),
+                   data_frame(index = seq_along(letters),
+                              letter = letters))
+})