title: R language - count of multiple columns group by one column
body: <p>I got data frame in R that looks like this:</p>
  
  <pre><code>&gt; df
     c1 c2 c3
  1: 10 c1 i1
  2: 10 c1 i2
  3: 10 c1 i3
  4: 10 c2 i1
  5: 10 c2 i2
  6: 10 c2 i3
  7: 20 c11 i1
  8: 20 c11 i2
  9: 20 c11 i3
  10: 20 c12 i1
  11: 20 c12 i2
  12: 20 c12 i3
  </code></pre>
  
  <p>I need to sum distinct counts of columns c2 and c3 group by c1 - to get the following result:</p>
  
  <pre><code>10 2 3
  20 2 3
  </code></pre>
  
  <p>How would I get that done in R?</p>
  
  <p>Thanks</p>