title: subset with pattern
body: <p>Say I have a data frame df</p>
  
  <pre><code>df &lt;- data.frame( a1 = 1:10, b1 = 2:11, c2 = 3:12 )
  </code></pre>
  
  <p>I wish to subset the columns, but with a pattern</p>
  
  <pre><code>df1 &lt;- subset( df, select= (pattern = "1") )
  </code></pre>
  
  <p>To get</p>
  
  <pre><code>&gt; df1
     a1 b1
  1   1  2
  2   2  3
  3   3  4
  4   4  5
  5   5  6
  6   6  7
  7   7  8
  8   8  9
  9   9 10
  10 10 11
  </code></pre>
  
  <p>Is this possible?</p>