title: Remove columns with zero values from a dataframe
body: <p>I have a data.frame: </p>
  
  <pre><code>SelectVar
       a   b  c   d   e   f   g   h   i j k l ll m n o p  q   r
  1 Dxa8 Dxa8 0 Dxa8 Dxa8 0 Dxa8 Dxa8 0 0 0 0  0 0 0 0 0 Dxc8 0
  2 Dxb8 Dxc8 0 Dxe8 Dxi8 0 tneg tpos 0 0 0 0  0 0 0 0 0 Dxi8 0
  </code></pre>
  
  <p>I would like to remove the columns with zero values in both rows from the data frame, so it yields a data frame as below:</p>
  
  <pre><code>SelectVar
       a   b    d    e    g   h     q   
  1 Dxa8 Dxa8 Dxa8 Dxa8 Dxa8 Dxa8  Dxc8 
  2 Dxb8 Dxc8 Dxe8 Dxi8 tneg tpos  Dxi8 
  </code></pre>
  
  <p>Have tried: </p>
  
  <pre><code>SelectVar!=0
  </code></pre>
  
  <p>which yields a True/False dataframe, and:</p>
  
  <pre><code>SelectVar[, colSums(abs(SelectVar)) ! == 0]
  </code></pre>
  
  <p>which yields an error. </p>
  
  <p>How could I remove the columns with zero values in each row?</p>