title: pair wise comparison, R code, vector
body: <p>I want to make pairwise comparisons of 13 data sets (13 independent experiments).  As the cell number differs among experiments it is required to correct the data with x value (the ratio of two cell population sizes).  The vector </p>
  
  <pre><code>cellno &lt;- c(2.3, 0.5, 1.3, 1.0, 1.6, 1.0, 1.0, 0.8, 1.2, 0.6, 0.8, 0.9, 0.9)
  </code></pre>
  
  <p>contains information about cell numbers.  So, I select first value from vector (i.e. 2.3) and divide each other number by 2.3 to get x.</p>
  
  <pre><code>n &lt;- cellno [1]
  for (i in n:length(cellno)) {print (cellno [i] / n)}
  </code></pre>
  
  <p>However, I want to calculate x for each pair of conditions one by one so I can then run my comparison function for those conditions. It means that I </p>
  
  <ul>
  <li>calculate x for condition 1 and 2 then make comparison of these conditions and then </li>
  <li>calculate x for condition 1 and 3 make comparison, </li>
  <li>calculate x for condition 1 and 4 and make comparison etc. </li>
  </ul>
  
  <p>When I am done with comparison of condition 1st with other 12 I would like to start the same for the condition 2nd etc. </p>