title: reshape data and coerce missing to zero
body: <p>EDIT:
  The original dataset can be found here: <a href="https://drive.google.com/file/d/0B4FnlzCZUFqWcHVVd3RXQnQwQzQ/view?usp=sharing" rel="nofollow">link</a></p>
  
  <p>I have a matrix like:</p>
  
  <pre><code>data &lt;- matrix(c("a","1","10",
               "b","1","20",
               "c","1","30",
               "a","2","10",
               "b","2","20",
               "a","3","10",
               "c","3","20"),
               ncol=3, byrow=TRUE)
  </code></pre>
  
  <p>I would like to reshape as a dataframe coercing the missing values to zero:</p>
  
  <pre><code>data &lt;- matrix(c("a","1","10",
               "b","1","20",
               "c","1","30",
               "a","2","10",
               "b","2","20",
               "c","2","0",
               "a","3","10",
               "b","3","0",
               "c","3","20"),
               ncol=3, byrow=TRUE)
  </code></pre>
  
  <p>How can I do it with the reshape package?
  Thaks</p>