title: Select every nth column in R from position x
body: <p>Imagine data is</p>
  <pre><code>v1&lt;-c(1,2,3)
  v2&lt;-c(3,1,2)
  v3&lt;-c(5,4,3)
  v4&lt;-c(2,3,2)
  v5&lt;-c(6,2,1)
  v6&lt;-c(1,1,2)
  v7&lt;-c(2,2,1)
  mydata&lt;-data.frame(v1,v2,v3,v4,v5,v6,v7)
  </code></pre>
  <p>I would like every other column from position v3.</p>
  <pre><code>  v3 v5 v7
  1  5  6  2
  2  4  2  2
  3  3  1  1
  </code></pre>
  <p>I am not sure how to use seq() from a certain position instead of the starting from the first column.</p>