Train identity scales when they have a guide.

Fixes tidyverse#453
kohske · Apr 27, 2012 · 7c7a228 · 7c7a228
1 parent 3852c08
commit 7c7a228
Show file tree

Hide file tree

Showing 3 changed files with 18 additions and 8 deletions.
diff --git a/NEWS b/NEWS
@@ -25,6 +25,10 @@ BUG FIXES
   triggered when scale was limited to a range smaller than the range of
   the data. (Bug reported by Tao Gao; diagnosed and fixed by Brian Diggs)
 
+* `scale_*_identity` will now produce a legend when `guide = "legend"` and no
+  breaks or labels are supplied (Fixes #453)
+
+
 ggplot2 0.9.0
 ----------------------------------------------------------------
 

diff --git a/R/scale-identity.r b/R/scale-identity.r
@@ -10,11 +10,13 @@
 #' qplot(1:4, 1:4, fill = colour, geom = "tile")
 #' qplot(1:4, 1:4, fill = colour, geom = "tile") + scale_fill_identity()
 #' 
-#' # To get a legend guide, you also need to supply labels, and specify 
-#' # guide = "legend"
-#' qplot(1:4, 1:4, fill = colour, geom = "tile") +
+#' # To get a legend guide, specify guide = "legend"
+#' qplot(1:4, 1:4, fill = colour, geom = "tile") + 
+#'   scale_fill_identity(guide = "legend")
+#' # But you'll typically also need to supply breaks and labels:
+#' qplot(1:4, 1:4, fill = colour, geom = "tile") + 
 #'   scale_fill_identity("trt", labels = letters[1:4], breaks = colour, 
-#'    guide = "legend")
+#'   guide = "legend")
 #' 
 #' # cyl scaled to appropriate size
 #' qplot(mpg, wt, data = mtcars, size = cyl)
@@ -72,7 +74,9 @@ scale_map.identity <- function(scale, x) {
 }
 #' @S3method scale_train identity
 scale_train.identity <- function(scale, x) {
-  # do nothing
+  # do nothing if no guide, otherwise train so we know what breaks to use
+  if (scale$guide == "none") return()
+  NextMethod()
 }
 
 icon.identity <- function() textGrob("f(x) = x", gp=gpar(cex=1.2))
diff --git a/man/scale_identity.Rd b/man/scale_identity.Rd
@@ -38,11 +38,13 @@ colour <- c("red", "green", "blue", "yellow")
 qplot(1:4, 1:4, fill = colour, geom = "tile")
 qplot(1:4, 1:4, fill = colour, geom = "tile") + scale_fill_identity()
 
-# To get a legend guide, you also need to supply labels, and specify
-# guide = "legend"
+# To get a legend guide, specify guide = "legend"
+qplot(1:4, 1:4, fill = colour, geom = "tile") +
+  scale_fill_identity(guide = "legend")
+# But you'll typically also need to supply breaks and labels:
 qplot(1:4, 1:4, fill = colour, geom = "tile") +
   scale_fill_identity("trt", labels = letters[1:4], breaks = colour,
-   guide = "legend")
+  guide = "legend")
 
 # cyl scaled to appropriate size
 qplot(mpg, wt, data = mtcars, size = cyl)