Generalize position_jitterdodge to all possible dodge positions

Fixes #1494

Author: hadley

NEWS.md

@@ -9,6 +9,9 @@
 
 * All `\donttest{}` examples run.
 
+* `position_jitterdodge()` now works on all possible dodge aesthetics, 
+ e.g. `color`, `linetype` etc. instead of only based on `fill` (@bleutner)
+
 * Removed a superfluous comma in `theme-defaults.r` code (@jschoeley)
 
 * Fixed a compatibility issue with `ggproto` and R versions prior to 3.1.2.

R/position-jitterdodge.R

@@ -35,17 +35,22 @@ PositionJitterdodge <- ggproto("PositionJitterdodge", Position,
   jitter.height = NULL,
   dodge.width = NULL,
 
-  required_aes = c("x", "y", "fill"),
+  required_aes = c("x", "y"),
 
   setup_params = function(self, data) {
     width <- self$jitter.width %||% resolution(data$x, zero = FALSE) * 0.4
-    # Adjust the x transformation based on the number of 'fill' variables
-    nfill <- length(levels(data$fill))
-
+    # Adjust the x transformation based on the number of 'dodge' variables
+    dodgecols <- intersect(c("fill", "colour", "linetype", "shape", "size", "alpha"), colnames(data))  
+    if (length(dodgecols) == 0) {
+      stop("`position_jitterdodge()` requires at least one aesthetic to dodge by", call. = FALSE)
+    }
+    ndodge    <- lapply(data[dodgecols], levels)  # returns NULL for numeric, i.e. non-dodge layers
+    ndodge    <- length(unique(unlist(ndodge)))
+    
     list(
       dodge.width = self$dodge.width,
       jitter.height = self$jitter.height,
-      jitter.width = width / (nfill + 2)
+      jitter.width = width / (ndodge + 2)
     )
   },