device parameter supports character argument

Parameter `device` now supports character argument to specify which
supported
  device to use ('pdf', 'png', 'jpeg', etc.), for when it cannot be
correctly
  inferred from the file extension (for example when a temporay
filename is
  supplied server side in shiny apps)

Author: Sebastian Kopf

NEWS

@@ -1,6 +1,11 @@
 ggplot2 0.9.3.1.99
 ----------------------------------------------------------------
 
+* Parameter `device` now supports character argument to specify which supported
+  device to use ('pdf', 'png', 'jpeg', etc.), for when it cannot be correctly
+  inferred from the file extension (for example when a temporay filename is
+  supplied server side in shiny apps) (@sebkopf, #939)
+
 * New `aes_q()` function to generate aesthetic specifications from
   quoted calls/names. `aes_string()` uses names `x` and `y` for first
   two unnamed arguments.

R/save.r

@@ -11,7 +11,9 @@
 #'
 #' @param filename file name/filename of plot
 #' @param plot plot to save, defaults to last plot displayed
-#' @param device device to use, automatically extract from file name extension
+#' @param device device to use, can be a function or any of the currently
+#' recognized extensions (\code{"pdf"}, \code{"jpeg"}, etc.), defaults to 
+#' automatically inferring the correct device from the file name
 #' @param path path to save plot to (if you just want to set path and not
 #'    filename)
 #' @param scale scaling factor
@@ -32,6 +34,9 @@
 #' ggsave("length-hist.png")
 #' ggsave("ratings.pdf", ratings)
 #' ggsave("ratings.pdf", ratings, width=4, height=4)
+#' # specify device when saving to a file with unknown extension 
+#' # (for example a server supplied temporary file)
+#' ggsave(tempfile(), device = "pdf")
 #' # make twice as big as on screen
 #' ggsave("ratings.pdf", ratings, scale=2)
 #' }
@@ -72,9 +77,22 @@ ggsave <- function(filename = default_name(plot), plot = last_plot(),
   default_device <- function(filename) {
     pieces <- strsplit(filename, "\\.")[[1]]
     ext <- tolower(pieces[length(pieces)])
-    match.fun(ext)
+    match_device(ext)
   }
 
+  match_device <- function(ext) {
+    if(!exists(ext, mode = "function")) {
+      stop("No graphics device defined for the file extension '", ext, "'. ", 
+           "Make sure to specify a filename with supported extension or ",
+           "set the device parameter.")
+    }
+    match.fun(ext)
+  }
+  
+  if (is.character(device)) {
+    device <- match_device(device)
+  }
+  
   units <- match.arg(units)
   convert_to_inches <- function(x, units) {
     x <- switch(units,

man/ggsave.Rd

@@ -13,8 +13,11 @@ ggsave(filename = default_name(plot), plot = last_plot(),
 
 \item{plot}{plot to save, defaults to last plot displayed}
 
-\item{device}{device to use, automatically extract from file name extension}
-
+\item{device}{device to use, can be a function or any of
+the currently recognized extensions (\code{"pdf"},
+\code{"jpeg"}, etc.), defaults to automatically inferring
+the correct device from the file name}
+  
 \item{path}{path to save plot to (if you just want to set path and not
 filename)}
 
@@ -53,6 +56,9 @@ ggsave("length-hist.pdf")
 ggsave("length-hist.png")
 ggsave("ratings.pdf", ratings)
 ggsave("ratings.pdf", ratings, width=4, height=4)
+# specify device when saving to a file with unknown extension
+# (for example a server supplied temporary file)
+ggsave(tempfile(), device = "pdf")
 # make twice as big as on screen
 ggsave("ratings.pdf", ratings, scale=2)
 }