title: trace the column following the string column for given dataset
body: <p>Looking for generic logic which can be applied to any dataset for finding the column which falls next to string column.</p>
  <p>Problem:
  Sum of first column and the column following the one with the string datatype = 5th column</p>
  <pre><code>{
  [10, 20, 'tyh', 30], 
  [66, 88, 'ltk', 99],
  [41, 31, 'qed', 11]
  }
  </code></pre>
  <p>Expected output:</p>
  <pre><code>{
  [10, 20, 'tyh', 30, 40], 
  [66, 88, 'ltk', 99, 165],
  [41, 31, 'qed', 11 , 52]
  }
  </code></pre>
  <p>The logic should work for below df also</p>
  <pre><code>{
  [111, 'tfy', 122, 133],
  [167, 'elt', 187, 197],
  [143, 'xqe', 132, 112]
  }
  </code></pre>
  <p>expected output :</p>
  <pre><code>{
  [111, 'tfy', 122, 133 , 244],
  [167, 'elt', 187, 197 , 364],
  [143, 'xqe', 132, 112, 255]
  }
  </code></pre>
  <p>what I did so far:</p>
  <pre><code>data[4]= data[0]+data[3] 
  </code></pre>
  <p>but this is hard coded and so wont work for second df.</p>