title: How select columns, where the first row equals TRUE in R?
body: <p>I am using following code</p>
  <pre><code>summary.out$which[which.max(summary.out$adjr2),]
  </code></pre>
  <p>This gives me column names with one one row, which equals to TRUE or FALSE.
  What should I add to this code in order to get column names, where the first row shows TRUE?
  Additionally, how can I create that all column names of this output are in one string deliminated with &quot;+&quot; sign? (one string showing &quot;Column1&quot;+&quot;Column2&quot;+&quot;Column3&quot;</p>