title: Normalizing data by reducing the sum
body: <p>I would like to normalize data (consisting of ID and samples with number of species) column-wise by randomly reducing the sum, which is now different in every column, to reach a sum of 100 in each column. Here is an example of a table:</p>
  
  <pre><code>   ID   S1   S2   S3
  1  1    0    0    3
  2  2    0    0    0
  3  3 5377 6140 7668
  4  4  288  416 1121
  5  5  876  786 1979
  6  6  407  522 3792
  </code></pre>
  
  <p>Only values >0 should be taken into account, as the species number cannot be negative. I would appreciate any ideas!</p>