title: How to melt and cast dataframes using dplyr?
body: <p>Recently I am doing all my data manipulations using dplyr and it is an excellent tool for that. However I am unable to melt or cast a data frame using dplyr. Is there any way to do that? Right now I am using reshape2 for this purpose.</p>
  
  <p>I want 'dplyr' solution for:</p>
  
  <pre><code>require(reshape2)
  data(iris)
  dat &lt;- melt(iris,id.vars="Species")
  </code></pre>