geom_polygon: make sure id is a factor/numeric

polygonGrob requires that `id` is numeric, but the value passed to it,
munched$group, was sometimes a character vector. Converting to a factor
ensures that it's numeric.

Author: wch

R/geom-polygon.r

@@ -58,6 +58,11 @@ GeomPolygon <- proto(Geom, {
   draw <- function(., data, scales, coordinates, ...) {
     n <- nrow(data)
     if (n == 1) return()
+
+    # Check if group is numeric, to make polygonGrob happy (factors are numeric,
+    # but is.numeric() will report FALSE because it actually checks something else)
+    if (mode(data$group) != "numeric")
+      data$group <- factor(data$group)
 
     munched <- coord_munch(coordinates, data, scales)
     # Sort by group to make sure that colors, fill, etc. come in same order

R/stat-contour.r

@@ -111,13 +111,15 @@ contour_lines <- function(data, breaks, complete = FALSE) {
   xs <- unlist(lapply(cl, "[[", "x"), use.names = FALSE)
   ys <- unlist(lapply(cl, "[[", "y"), use.names = FALSE)
   pieces <- rep(seq_along(cl), lengths)
-  
+  # Add leading zeros so that groups can be properly sorted later
+  groups <- paste(data$group[1], sprintf("%03d", pieces), sep = "-")
+
   data.frame(
     level = rep(levels, lengths),
     x = xs,
     y = ys,
     piece = pieces,
-    group = paste(data$group[1], pieces, sep = "-")
+    group = groups
   )
 }