Expand binwidth when needed

Fixes #1610

Author: hadley

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 2.1.0.9000 
 
+* `stat_bin()` and `stat_summary_hex()` now accept length 1 `binwidth` (#1610)
+
 * `geom_histogram()` and `stat_bin()` understand the `breaks` parameter once 
   more. (#1665).
 

R/hexbin.R

@@ -13,6 +13,10 @@ hex_bounds <- function(x, binwidth) {
 }
 
 hexBinSummarise <- function(x, y, z, binwidth, fun = mean, fun.args = list(), drop = TRUE) {
+  if (length(binwidth) == 1) {
+    binwidth <- rep(binwidth, 2)
+  }
+
   # Convert binwidths into bounds + nbins
   xbnds <- hex_bounds(x, binwidth[1])
   xbins <- diff(xbnds) / binwidth[1]

tests/testthat/test-stat-hex.R

@@ -0,0 +1,8 @@
+context("stat-hex")
+
+test_that("can use length 1 binwidth", {
+  df <- data.frame(x = c(1, 1, 2), y = c(1, 1, 2))
+  p <- ggplot(df, aes(x, y)) + stat_binhex(binwidth = 1)
+
+  expect_equal(nrow(layer_data(p)), 2)
+})