Add a blank layer to empty plots

Author: hadley

NEWS

@@ -1,6 +1,9 @@
 ggplot2 1.0.1.9xxx
 ----------------------------------------------------------------
 
+* ggplot no longer throws an error if you your plot doesn't have any
+  layers.  Instead it automatically adds `geom_blank()` (#1246)
+
 * `geom_smooth()` is no longer so chatty. If you want to know what the deafult
   smoothing method is, look it up in the documentation! (#1247)
 

R/geom-blank.r

@@ -23,7 +23,7 @@
 #' c + geom_abline(aes(intercept = a, slope = b), data = df)
 geom_blank <- function(mapping = NULL, data = NULL, stat = "identity",
                        position = "identity", show.legend = NA,
-                       inherit.aes = FALSE, ...) {
+                       inherit.aes = TRUE, ...) {
   layer(
     data = data,
     mapping = mapping,

R/limits.r

@@ -128,5 +128,5 @@ limits.POSIXlt <- function(lims, var) {
 expand_limits <- function(...) {
   data <- data.frame(..., stringsAsFactors = FALSE)
 
-  geom_blank(aes_all(names(data)), data)
+  geom_blank(aes_all(names(data)), data, inherit.aes = FALSE)
 }

R/plot-build.r

@@ -12,9 +12,11 @@
 #' @keywords internal
 #' @export
 ggplot_build <- function(plot) {
-  if (length(plot$layers) == 0) stop("No layers in plot", call. = FALSE)
-
   plot <- plot_clone(plot)
+  if (length(plot$layers) == 0) {
+    plot <- plot + geom_blank()
+  }
+
   layers <- plot$layers
   layer_data <- lapply(layers, function(y) y$data)
 

man/geom_blank.Rd

@@ -5,7 +5,7 @@
 \title{Blank, draws nothing.}
 \usage{
 geom_blank(mapping = NULL, data = NULL, stat = "identity",
-  position = "identity", show.legend = NA, inherit.aes = FALSE, ...)
+  position = "identity", show.legend = NA, inherit.aes = TRUE, ...)
 }
 \arguments{
 \item{mapping}{The aesthetic mapping, usually constructed with