title: R data frame - aggregating multiple columns at once
body: <p>With a data frame df like below</p>
  
  <pre><code>----------------------
  a     |  b    |  c 
  ------+-------+-------
  true  | true  | true
  false | true  | false
  false | false | false
  true  | true  | false
  </code></pre>
  
  <p>I need to find the % of <code>"true"</code> for each of the columns a, b and c as a data frame such that it can be used in a ggplot. How to go about it ? </p>
  
  <p>Note:- <code>"true"</code> is not the logical <code>TRUE</code></p>