Allow NA values in position_dodge2 (#4408)

Author: thomasp85

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* Fix a bug in `position_dodge2()` where `NA` values in thee data would cause an
+  error (@thomasp85, #2905)
+
 * Fix a bug in `position_jitter()` where different jitters would be applied to 
   different position aesthetics of the same axis (@thomasp85, #2941)
 

R/position-dodge2.r

@@ -138,7 +138,7 @@ find_x_overlaps <- function(df) {
   overlaps[1] <- counter <- 1
 
   for (i in seq_asc(2, nrow(df))) {
-    if (df$xmin[i] >= df$xmax[i - 1]) {
+    if (is.na(df$xmin[i]) || is.na(df$xmax[i - 1]) || df$xmin[i] >= df$xmax[i - 1]) {
       counter <- counter + 1
     }
     overlaps[i] <- counter

tests/testthat/test-position-dodge2.R

@@ -107,3 +107,11 @@ test_that("width of groups is computed per facet", {
 
   expect_true(all(width == (0.9 / 3) * 0.9))
 })
+
+test_that("NA values are given their own group", {
+  df <- data.frame(
+    xmin = c(1, 2, NA, NA),
+    xmax = c(1, 2, NA, NA)
+  )
+  expect_equal(find_x_overlaps(df), seq_len(4))
+})