title: errors using multi plot (ggplot2) and grid.arrange (gridExtra)
body: <p>I am trying to make a graph with three panels. I am trying to use the functions multi plot (of ggplot2) and grid.arrange of (of gridExtra). None of them work! 
  How could I fix this problem???</p>
  
  <pre><code>multiplot(f1.1,f1.2,f1.3)
  Error: could not find function "multiplot"
  
  grid.arrange(f1.1,f1.2,f1.3)
  Error: No layers in plot
  </code></pre>