scale_size_area: default to area proportional to data value

DESCRIPTION

@@ -23,7 +23,7 @@ Imports:
     grid,
     gtable (>= 0.1.1),
     reshape2,
-    scales (>= 0.2.2),
+    scales (>= 0.2.2.99.1),
     proto,
     MASS
 Suggests:

R/scale-area.r

@@ -1,9 +1,18 @@
 #' Scale area instead of radius (for size).
 #'
+#' \code{\link{scale_area}} is deprecated and will be removed in a future
+#' version of ggplot2. Use \code{\link{scale_size_area}} instead. Note that the
+#' default behavir of \code{\link{scale_size_area}} is slightly different: by
+#' default, it makes the area proportional to the numeric value.
+#'
 #' @param ... Other arguments passed on to \code{\link{continuous_scale}} 
 #'   to control name, limits, breaks, labels and so forth.
 #' @param range Range of output sizes.  Should be greater than 0.
 #' @export
 scale_area <- function(..., range = c(1, 6)) {
+  message("scale_area is deprecated and will be removed in a future version of ggplot2.\n",
+    "  Use scale_size_area instead. Note that the behavior of scale_size_area is\n",
+    "  slightly different: by default it makes the area proportional to the\n",
+    "  numeric value.")
   continuous_scale("size", "area", area_pal(range), ...)
 }

R/scale-size.r

@@ -44,3 +44,23 @@ scale_size_discrete <- function(..., range = c(1, 6)) {
   discrete_scale("size", "size_d",
     function(n) seq(range[1], range[2], length = n), ...)
 }
+
+#' Scale area instead of radius, for size.
+#'
+#' When \code{scale_size_area} is used, the default behavior is to scale the
+#' area of points to be proportional to the value.
+#'
+#' Note that this controls the size scale, so it will also control
+#' the thickness of lines. Line thickness will be proportional to the square
+#' root of the value, which is probably undesirable in most cases.
+#'
+#' @param ... Other arguments passed on to \code{\link{continuous_scale}}
+#'   to control name, limits, breaks, labels and so forth.
+#' @param range Range of output sizes.  Should be greater than 0.
+#' @param max_size Size of largest points.
+#' @export
+scale_size_area <- function(..., max_size = 6) {
+  continuous_scale("size", "area",
+    pal = abs_area(max_size),
+    rescaler = rescale_max, ...)
+}