title: Insert an empty column between every column of a dataframe in R
body: <p>Say you have a dataframe of four columns:</p>
  
  <pre><code>dat &lt;- data.frame(A = rnorm(5), B = rnorm(5), C = rnorm(5), D = rnorm(5))
  </code></pre>
  
  <p>And you want to insert an empty column between each of the columns in the dataframe, so that the output is:</p>
  
  <pre><code>           A A1           B B1          C C1           D D1
  1 1.15660588 NA  0.78350197 NA -0.2098506 NA  2.07495662 NA
  2 0.60107853 NA  0.03517539 NA -0.4119263 NA -0.08155673 NA
  3 0.99680981 NA -0.83796981 NA  1.2742644 NA  0.67469277 NA
  4 0.09940946 NA -0.89804952 NA  0.3419173 NA -0.95347049 NA
  5 0.28270734 NA -0.57175554 NA -0.4889045 NA -0.11473839 NA
  </code></pre>
  
  <p>How would you do this?  </p>
  
  <p>The dataframe I would like to do this operation to has hundreds of columns and so obviously I don't want to type out each column and add them naively like this:</p>
  
  <pre><code>dat$A1 &lt;- NA
  dat$B1 &lt;- NA
  dat$C1 &lt;- NA
  dat$D1 &lt;- NA
  
  dat &lt;- dat[, c("A", "A1", "B", "B1", "C", "C1", "D", "D1")]
  </code></pre>
  
  <p>Thanks for you help in advance!</p>