title: multiply all the columns in a data.frame by the first
body: <p>I need to multiply each column in a <code>data.frame</code>by the values in first column (classfactor).</p>
  
  <p>This is my <code>data.frame</code></p>
  
  <pre><code>sample classfactor 01.BA.V 01.BA.VG 01.BO.VG 01.PR.O 01.TO.VG 02.BA.O 02.BA.V
  AB 0.730 0.000000000 0.000000000 0.000000000 0.000000000 0.000000000 0 0.00000000
  AC 0.730 0.000000000 0.000000000 0.000000000 0.000000000 0.000000000 0 0.00000000
  AB 0.002 0.000000000 0.000000000 0.000749929 0.000000000 0.000000000 0 0.00000000
  CC 0.730 0.081599145 0.093453018 0.031247022 0.015987076 0.036212483 0 0.02537884
  BB 0.730 0.000000000 0.000000000 0.000000000 0.000000000 0.000000000 0 0.00000000
  AA 0.730 0.001533075 0.000108666 0.000000000 0.000364526 0.000241417 0 0.00006340
  </code></pre>
  
  <p>It has 146 rows and 155 columns.</p>
  
  <p>I can't figure out how to do. Any suggestions?</p>