Pass on binwidth and height to geom

NEWS.md

@@ -1,5 +1,10 @@
 # ggplot2 (development version)
 
+* `geom_hex()` will now use the binwidth from `stat_bin_hex()` if present, 
+  instead of deriving it (@thomasp85, #4580)
+
+* `geom_hex()` now works on non-linear coordinate systems (@thomasp85)
+
 * Fixed a bug throwing errors when trying to render an empty plot with secondary
   axes (@thomasp85, #4509)
 

R/geom-hex.r

@@ -56,12 +56,36 @@ geom_hex <- function(mapping = NULL, data = NULL,
 GeomHex <- ggproto("GeomHex", Geom,
   draw_group = function(data, panel_params, coord, lineend = "butt",
                         linejoin = "mitre", linemitre = 10) {
-    if (!inherits(coord, "CoordCartesian")) {
-      abort("geom_hex() only works with Cartesian coordinates")
+    if (empty(data)) {
+      return(zeroGrob())
     }
 
+    # Get hex sizes
+    if (!is.null(data$width)) {
+      dx <- data$width[1] / 2
+    } else {
+      dx <- resolution(data$x, FALSE)
+    }
+    # Adjust for difference in width and height of regular hexagon. 1.15 adjusts
+    # for the effect of the overlapping range in y-direction on the resolution
+    # calculation
+    if (!is.null(data$height)) {
+      dy <- data$height[1] /  sqrt(3) / 2
+    } else {
+      dy <- resolution(data$y, FALSE) / sqrt(3) / 2 * 1.15
+    }
+
+    hexC <- hexbin::hexcoords(dx, dy, n = 1)
+
+    n <- nrow(data)
+
+    data <- data[rep(seq_len(n), each = 6), ]
+    data$x <- rep.int(hexC$x, n) + data$x
+    data$y <- rep.int(hexC$y, n) + data$y
+
     coords <- coord$transform(data, panel_params)
-    ggname("geom_hex", hexGrob(
+
+    ggname("geom_hex", polygonGrob(
       coords$x, coords$y,
       gp = gpar(
         col = coords$colour,
@@ -71,7 +95,9 @@ GeomHex <- ggproto("GeomHex", Geom,
         lineend = lineend,
         linejoin = linejoin,
         linemitre = linemitre
-      )
+      ),
+      default.units = "native",
+      id.lengths = rep.int(6, n)
     ))
   },
 
@@ -97,6 +123,8 @@ GeomHex <- ggproto("GeomHex", Geom,
 # @param size vector of hex sizes
 # @param gp graphical parameters
 # @keyword internal
+#
+# THIS IS NO LONGER USED BUT LEFT IF CODE SOMEWHERE ELSE RELIES ON IT
 hexGrob <- function(x, y, size = rep(1, length(x)), gp = gpar()) {
   if (length(y) != length(x)) abort("`x` and `y` must have the same length")
 

R/hexbin.R

@@ -36,6 +36,8 @@ hexBinSummarise <- function(x, y, z, binwidth, fun = mean, fun.args = list(), dr
   # Convert to data frame
   out <- new_data_frame(hexbin::hcell2xy(hb))
   out$value <- as.vector(value)
+  out$width <- binwidth[1]
+  out$height <- binwidth[2]
 
   if (drop) out <- stats::na.omit(out)
   out

tests/testthat/test-geom-hex.R

@@ -15,6 +15,25 @@ test_that("size and linetype are applied", {
     geom_hex(color = "red", size = 4, linetype = 2)
 
   gpar <- layer_grob(plot)[[1]]$children[[1]]$gp
-  expect_equal(gpar$lwd, c(4, 4) * .pt, tolerance = 1e-7)
-  expect_equal(gpar$lty, c(2, 2), tolerance = 1e-7)
+  expect_equal(gpar$lwd, rep(4, 12) * .pt, tolerance = 1e-7)
+  expect_equal(gpar$lty, rep(2, 12), tolerance = 1e-7)
+})
+
+test_that("bin size are picked up from stat", {
+  expect_doppelganger("single hex bin with width and height of 0.1",
+    ggplot(data.frame(x = 0, y = 0)) +
+      geom_hex(aes(x = x, y = y), binwidth = c(0.1, 0.1)) +
+      coord_cartesian(xlim = c(-1, 1), ylim = c(-1, 1))
+  )
+})
+
+test_that("geom_hex works in non-linear coordinate systems", {
+  p <- ggplot(mpg, aes(displ, hwy)) + geom_hex()
+
+  expect_doppelganger("hex bin plot with sqrt-transformed y",
+    p + coord_trans(y = "sqrt")
+  )
+  expect_doppelganger("hex bin plot in polar coordinates",
+                      p + coord_polar()
+  )
 })