Implement degree_format() (#159) (#178)

* Implement degree_format()

* Fix typo in examples

* Add NEWS bullet

NAMESPACE

@@ -44,6 +44,7 @@ export(cscale)
 export(date_breaks)
 export(date_format)
 export(date_trans)
+export(degree_format)
 export(dichromat_pal)
 export(discard)
 export(div_gradient_pal)

NEWS.md

@@ -1,5 +1,7 @@
 # scales 1.0.0.9000
 
+* New `degree_format()` adds degree symbols to numbers (@mikmart, #159).
+
 * `number_bytes()` now:
 
     1. Always uses "B" as the symbol for bytes (#174).

R/formatter.r

@@ -251,6 +251,32 @@ unit_format <- function(accuracy = 1, scale = 1, prefix = "",
   )
 }
 
+#' @rdname number_format
+#' @export
+#' @examples
+#' # degree_format()
+#' celcius <- degree_format(unit = "C")
+#' celcius(rnorm(10) * 10)
+#'
+#' west <- degree_format(unit = "W")
+#' west(runif(10) * 100)
+degree_format <- function(accuracy = 1, scale = 1, prefix = "",
+                          unit = "", sep = "",
+                          suffix = paste0(sep, "\u00b0", unit),
+                          big.mark = " ", decimal.mark = ".",
+                          trim = TRUE, ...) {
+  number_format(
+    accuracy = accuracy,
+    scale = scale,
+    prefix = prefix,
+    suffix = suffix,
+    big.mark = big.mark,
+    decimal.mark = decimal.mark,
+    trim = trim,
+    ...
+  )
+}
+
 #' @rdname number_format
 #' @export
 number_si <- function(x, prefix = "", suffix = "", ...) {

tests/testthat/test-formatter.r

@@ -158,6 +158,20 @@ test_that("unit format", {
   )
 })
 
+
+# Degree formatter --------------------------------------------------------
+
+test_that("Degree format adds degree symbol", {
+  degree <- degree_format()
+  expect_equal(degree(c(-10, 0, 20, NA)), c("-10°", "0°", "20°", "NA°"))
+})
+
+test_that("Degree format can also add unit symbols", {
+  celcius <- degree_format(unit = "C")
+  expect_equal(celcius(c(-10, 0, 20)), c("-10°C", "0°C", "20°C"))
+})
+
+
 # Percent formatter -------------------------------------------------------
 
 test_that("negative percents work", {