title: Divide multiple columns with dplyr in R
body: <p>My data frame looks like this, but I have hundreds of columns</p>
  <pre><code>t1 &lt;- c(11,2,3,4)
  t2 &lt;- c(10,2,3,4)
  total1 &lt;- c(8,2,3,4)
  total2 &lt;- c(4,6,3,4)
  test &lt;- data.frame(t1,t2,total1,total2)
    t1 t2 total1 total2
  1 11 10      8      4
  2  2  2      2      6
  3  3  3      3      3
  4  4  4      4      4
  </code></pre>
  <p>I want to divide the t1/total2 and make a new column called freq1
  and then t2/total2 and make a new column called freq2. I want to do this over hundreds
  of columns.</p>
  <p>I want my data to look like this</p>
  <pre><code>    t1 t2 total1 total2 freq1 freq2
  1   11 10    8      4    1.37 2.5
  2   2  2     2      6    1.    0.33
  3   3  3     3      3.   1.    1
  4   4  4     4      4.   1.    1
  </code></pre>
  <p>I am working like this</p>
  <pre><code>mutate(freq1= t1/total1)
  </code></pre>
  <p>But this is problematic. I can not do it for all columns.</p>