Merge pull request #5103 from teunbrand/date_bins

Binned scales and date(time) transformations

Author: teunbrand

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* Binned scales are now compatible with `trans = "date"` and `trans = "time"` 
+  (@teunbrand, #4217).
 * `ggsave()` warns when multiple `filename`s are given, and only writes to the
   first file (@teunbrand, #5114).
 * Fixed a regression in `geom_hex()` where aesthetics were replicated across 

R/scale-.r

@@ -1075,10 +1075,13 @@ ScaleBinned <- ggproto("ScaleBinned", Scale,
       # Ensure terminal bins are same width if limits not set
       if (is.null(self$limits)) {
         # Remove calculated breaks if they coincide with limits
-        breaks <- setdiff(breaks, limits)
+        breaks <- breaks[!breaks %in% limits]
         nbreaks <- length(breaks)
         if (nbreaks >= 2) {
-          new_limits <- c(2 * breaks[1] - breaks[2], 2 * breaks[nbreaks] - breaks[nbreaks - 1])
+          new_limits <- c(
+            breaks[1] + (breaks[1] - breaks[2]),
+            breaks[nbreaks] + (breaks[nbreaks] - breaks[nbreaks - 1])
+          )
           if (breaks[nbreaks] > limits[2]) {
             new_limits[2] <- breaks[nbreaks]
             breaks <- breaks[-nbreaks]

tests/testthat/test-scale-binned.R

@@ -4,3 +4,39 @@ test_that("binned scales only support continuous data", {
   p <- ggplot(mtcars) + geom_point(aes(disp, mpg, colour = as.character(gear))) + scale_color_binned()
   expect_snapshot_error(ggplot_build(p))
 })
+
+test_that('binned scales can calculate breaks on dates', {
+
+  data <- seq(as.Date("2000-01-01"), as.Date("2020-01-01"), length.out = 100)
+
+  scale <- scale_x_binned(trans = "date")
+  scale$train(scale$transform(data))
+  breaks <- scale$trans$inverse(scale$get_breaks())
+
+  expect_s3_class(breaks, "Date")
+  expect_equal(
+    unname(breaks),
+    as.Date(paste0(seq(2002, 2018, by = 2), "-01-01"))
+  )
+})
+
+test_that('binned scales can calculate breaks on date-times', {
+  data <- seq(
+    strptime("2000-01-01", "%Y-%m-%d"),
+    strptime("2020-01-01", "%Y-%m-%d"),
+    length.out = 100
+  )
+
+  scale <- scale_x_binned(trans = "time")
+  scale$train(scale$transform(data))
+  breaks <- scale$trans$inverse(scale$get_breaks())
+
+  expect_s3_class(breaks, "POSIXct")
+  expect_equal(
+    unname(unclass(breaks)),
+    unclass(as.POSIXct(strptime(
+      paste0(seq(2002, 2018, by = 2), "-01-01"),
+      "%Y-%m-%d"
+    )))
+  )
+})