title: Saving many subsets as dataframes using "for"-loops
body: <p>this question might be very simple, but I do not find a good way to solve it:
  I have a dataset with many subgroups which need to be analysed all-together and on their own. Therefore, I want to use subsets for the groups and use them for the later analysis. As well, the defintion of the subsets as the analysis should be partly done with loops in order to save space and to ensure that the same analysis has been done with all subgroups.</p>
  
  <p>Here is an example of my code using an example dataframe from the boot package:</p>
  
  <pre><code>data(aids)
  qlist &lt;- c("1","2","3","4")
  for (i in length(qlist)) {
      paste("aids.sub.",qlist[i],sep="") &lt;- subset(aids, quarter==qlist[i])
  }
  </code></pre>
  
  <p>The variable which contains the subgroups in my dataset is stored as a string, therefore I added the qlist part which would be not required otherwise.</p>