Allow use of position_stack() when ymax is NA (#3416, fixes #2709)

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* stacking text when calculating the labels and the y axis with
+  `stat_summary()` now works (@ikosmidis, #2709)
+
 * Allowed reversing of discrete scales by re-writing `get_limits()` (@AnneLyng, #3115)
 
 * Added `stat_contour_filled()` and `geom_contour_filled()`, which compute 

R/position-stack.r

@@ -177,6 +177,8 @@ PositionStack <- ggproto("PositionStack", Position,
     }
 
     negative <- data$ymax < 0
+    negative[is.na(negative)] <- FALSE
+
     neg <- data[negative, , drop = FALSE]
     pos <- data[!negative, , drop = FALSE]
 

tests/testthat/test-position-stack.R

@@ -52,3 +52,9 @@ test_that("data with no extent is stacked correctly", {
   expect_equal(layer_data(p0)$y, c(-75, -115))
   expect_equal(layer_data(p1)$y, c(0, -75))
 })
+
+test_that("position_stack() can stack correctly when ymax is NA", {
+  df <- data_frame(x = c(1, 1), y = c(1, 1))
+  p <- ggplot(df, aes(x, y, ymax = NA_real_)) + geom_point(position = "stack")
+  expect_equal(layer_data(p)$y, c(1, 2))
+})