title: Inserting date & time into WMF filename
body: <p>Creating some graphs, and want the date/time of creation to be in the filename.  I found the answers to <a href="https://stackoverflow.com/questions/5424648/add-date-and-time-to-pdf-output-file-name">this question</a> very helpful on that topic, and </p>
  
  <pre><code> paste("plotname",Sys.time(),".wmf",sep='')
  </code></pre>
  
  <p>does in fact spit out </p>
  
  <pre><code>[1] "plotname2013-07-02 11:55:04.wmf"
  </code></pre>
  
  <p>but </p>
  
  <pre><code>win.metafile(paste("plotname",Sys.time(),".wmf",sep=''))
  # win.metafile("test.wmf")
  ggplot(data.file, aes(x = group, y = delta)) + geom_boxplot()
  dev.off()
  </code></pre>
  
  <p>gives</p>
  
  <pre><code>Error in win.metafile(paste("plotname", Sys.time(), ".wmf", sep = "")) : unable to start win.metafile:plotname2013-07-02 11:56:23.wmf() device
  </code></pre>
  
  <p>where it works with the simpler win.metafile("test.wmf") command.  What's the problem here?</p>