Allow violins to scale freely.

Fixes #1388

Author: hadley

NAMESPACE

@@ -331,6 +331,7 @@ export(last_plot)
 export(layer)
 export(layer_data)
 export(layer_grob)
+export(layer_scales)
 export(lims)
 export(map_data)
 export(margin)

R/geom-violin.r

@@ -99,8 +99,6 @@ GeomViolin <- ggproto("GeomViolin", Geom,
 
     # ymin, ymax, xmin, and xmax define the bounding rectangle for each group
     plyr::ddply(data, "group", transform,
-      ymin = min(y),
-      ymax = max(y),
       xmin = x - width / 2,
       xmax = x + width / 2
     )

R/plot-build.r

@@ -3,9 +3,11 @@
 #' \code{ggplot_build} takes the plot object, and performs all steps necessary
 #' to produce an object that can be rendered.  This function outputs two pieces:
 #' a list of data frames (one for each layer), and a panel object, which
-#' contain all information about axis limits, breaks etc. \code{layer_data}
-#' and \code{layer_grob} are helper functions which returns the data or grob
-#' associated with a given layer.
+#' contain all information about axis limits, breaks etc.
+#'
+#' \code{layer_data}, \code{layer_grob}, and \code{layer_scales} are helper
+#' functions that returns the data, grob, or scales associated with a given
+#' layer. These are useful for tests.
 #'
 #' @param plot ggplot object
 #' @seealso \code{\link{print.ggplot}} and \code{\link{benchplot}} for
@@ -95,6 +97,20 @@ layer_data <- function(plot, i = 1L) {
   ggplot_build(plot)$data[[i]]
 }
 
+#' @export
+#' @rdname ggplot_build
+layer_scales <- function(plot, i = 1L, j = 1L) {
+  b <- ggplot_build(plot)
+
+  layout <- b$panel$layout
+  selected <- layout[layout$ROW == i & layout$COL == j, , drop = FALSE]
+
+  list(
+    x = b$panel$x_scales[[selected$SCALE_X]],
+    y = b$panel$y_scales[[selected$SCALE_Y]]
+  )
+}
+
 #' @export
 #' @rdname ggplot_build
 layer_grob <- function(plot, i = 1L) {

man/ggplot_build.Rd

@@ -1,5 +1,20 @@
 context("geom_violin")
 
+test_that("", {
+  df <- rbind(
+    data.frame(x = "a", y = c(0, runif(10), 1)),
+    data.frame(x = "b", y = c(0, runif(10), 2))
+  )
+
+  p <- ggplot(df, aes(1, y)) +
+    geom_violin() +
+    facet_grid(x ~ ., scales = "free") +
+    coord_cartesian(expand = FALSE)
+
+  expect_equal(layer_scales(p, 1)$y$dimension(), c(0, 1))
+  expect_equal(layer_scales(p, 2)$y$dimension(), c(0, 2))
+})
+
 # create_quantile_segment_frame -------------------------------------------------
 
 test_that("create_quantile_segment_frame functions for 3 quantiles", {