title: How to create modified column based on values
body: <p>A, B, C and D are input columns, </p>
  
  <p>Input:</p>
  
  <pre><code> A   B    C    D  
  SG   TC   Y1  8  
  SG   TC   Y2  2  
  SG   TC   Y3  12 
  SG1  TC   Y1  12 
  SG1  TC   Y2  2 
  SG1  TC   Y3  12 
  SG1  TC1  Y1  12 
  SG1  TC1  Y2  10 
  SG1  TC1  Y3  9 
  </code></pre>
  
  <p>Require output</p>
  
  <pre><code>A   B   C   D  Out put
  SG  TC  Y1  8  Y1+Y2
  SG  TC  Y2  2  Y1+Y2
  SG  TC  Y3  12 Y3
  SG1 TC  Y1  12 Y1+Y2
  SG1 TC  Y2  2  Y1+Y2
  SG1 TC  Y3  12 Y3
  SG1 TC1 Y1  12 Y1
  SG1 TC1 Y2  10 Y1+Y3
  SG1 TC1 Y3  9  Y1+Y3
  </code></pre>