Preserve NAs in x when zero range

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: scales
-Version: 0.2.5.9001
+Version: 0.2.5.9002
 Authors@R: c(
     person("Hadley", "Wickham", , "hadley@rstudio.com", c("aut", "cre")),
     person("RStudio", role = "cph")

NEWS

@@ -1,6 +1,9 @@
 Version 0.2.5.9000
 ------------------------------------------------------------------------------
 
+* `rescale()` preserves missing values in input when the range of `x` is
+  (effectively) 0 (ggplot2#985).
+
 * Continuous colour palettes now use `colour_ramp()` instead of `colorRamp()`.
   This only supports interpolation in Lab colour space, but is hundreds of
   times faster.

R/bounds.r

@@ -10,8 +10,10 @@
 #' rescale(1:100)
 #' rescale(runif(50))
 #' rescale(1)
-rescale <- function(x, to = c(0, 1), from = range(x, na.rm = TRUE)) {
-  if (zero_range(from) || zero_range(to)) return(rep(mean(to), length(x)))
+rescale <- function(x, to = c(0, 1), from = range(x, na.rm = TRUE, finite = TRUE)) {
+  if (zero_range(from) || zero_range(to)) {
+    return(ifelse(is.na(x), NA, mean(to)))
+  }
 
   (x - from[1]) / diff(from) * diff(to) + to[1]
 }

man/rescale.Rd

@@ -4,7 +4,7 @@
 \alias{rescale}
 \title{Rescale numeric vector to have specified minimum and maximum.}
 \usage{
-rescale(x, to = c(0, 1), from = range(x, na.rm = TRUE))
+rescale(x, to = c(0, 1), from = range(x, na.rm = TRUE, finite = TRUE))
 }
 \arguments{
 \item{x}{numeric vector of values to manipulate.}

tests/testthat/test-rescale.R

@@ -0,0 +1,5 @@
+context("rescale")
+
+test_that("rescale preserves NAs even when x has zero range", {
+  expect_equal(rescale(c(1, NA)), c(0.5, NA))
+})