title: How to generate a sequence including NA values in R?
body: <p>I want to know how to generate an automatized sequence from 0 to 100, with numbers each 5 positions only, all the rest should be NA values. At the end I would like to have something like this:</p>
  
  <pre><code>&gt; labCol
  [1]  0 NA NA NA NA  5 NA NA NA NA 10 NA NA NA NA 15 NA  .....  100
  </code></pre>
  
  <p>I have done this example manually like this, but it is time consuming:</p>
  
  <pre><code>labCol &lt;- c(0, NA, NA, NA, NA, 5, NA, NA, NA, NA, 10, NA, NA, NA, NA, 15, NA, ... 100 )
  </code></pre>
  
  <p>I can't find an option in the <code>seq()</code> function to do this.</p>
  
  <p>This problem is because I'm doing a Heat Map with the function <code>heatmap.2()</code> of the <code>gplots</code> package, and the column labels are too close to read. Neither can I set the labels every 5 or 10 positions. That is why I need generate my own label sequence with NA values to avoid this overlapping.</p>
  
  <p>Any suggestion is welcome :)</p>