guides-axis: make assignment a bit more elegant

Author: Rasmus

R/guides-axis.r

@@ -14,12 +14,22 @@ guide_axis <- function(at, labels, position = "right", theme) {
   zero <- unit(0, "npc")
   one <- unit(1, "npc")
 
-  theme$axis.ticks.length.x <- theme$axis.ticks.length.x %||% theme$axis.ticks.length
-  theme$axis.ticks.length.x.bottom <- theme$axis.ticks.length.x.bottom %||% theme$axis.ticks.length.x
-  theme$axis.ticks.length.x.top <- theme$axis.ticks.length.x.top %||% theme$axis.ticks.length.x
-  theme$axis.ticks.length.y <- theme$axis.ticks.length.y %||% theme$axis.ticks.length
-  theme$axis.ticks.length.y.left <- theme$axis.ticks.length.y.left %||% theme$axis.ticks.length.y
-  theme$axis.ticks.length.y.right <- theme$axis.ticks.length.y.right %||% theme$axis.ticks.length.y
+  theme$axis.ticks.length.x.bottom <- with(theme,
+                                           axis.ticks.length.x.bottom %||%
+                                           axis.ticks.length.x %||%
+                                           axis.ticks.length)
+  theme$axis.ticks.length.x.top <- with(theme,
+                                        axis.ticks.length.x.top %||%
+                                        axis.ticks.length.x %||%
+                                        axis.ticks.length)
+  theme$axis.ticks.length.y.left <- with(theme,
+                                         axis.ticks.length.y.left %||%
+                                         axis.ticks.length.y %||%
+                                         axis.ticks.length)
+  theme$axis.ticks.length.y.right <- with(theme,
+                                          axis.ticks.length.y.right %||%
+                                          axis.ticks.length.y %||%
+                                          axis.ticks.length)
 
   label_render <- switch(position,
     top = "axis.text.x.top", bottom = "axis.text.x.bottom",