title: How to extend the 'summary' function to include sd, kurtosis and skew?
body: <p>R's <code>summary</code> function works really well on a dataframe, giving, for example:</p>
  
  <pre><code>&gt; summary(fred)
     sum.count          count              sum              value      
   Min.   : 1.000   Min.   :    1.0   Min.   :      1   Min.   : 0.00  
   1st Qu.: 1.000   1st Qu.:    6.0   1st Qu.:      7   1st Qu.:35.82  
   Median : 1.067   Median :    9.0   Median :     10   Median :42.17  
   Mean   : 1.238   Mean   :  497.1   Mean   :   6120   Mean   :43.44  
   3rd Qu.: 1.200   3rd Qu.:   35.0   3rd Qu.:     40   3rd Qu.:51.31  
   Max.   :40.687   Max.   :64425.0   Max.   :2621278   Max.   :75.95
  </code></pre>
  
  <p>What I'd like to do is modify the function so it also gives, after 'Mean', an entry for the standard deviation, the kurtosis and the skew.</p>
  
  <p>What's the best way to do this? I've researched this a bit, and adding a function with a method doesn't  work for me:</p>
  
  <pre><code>&gt; summary.class &lt;- function(x)
  {
    return(sd(x))
  }
  </code></pre>
  
  <p>The above is just ignored. I suppose that I need to understand how to define all classes to return.</p>