title: Dropping NAS from columns and rows at the same time
body: <p>Working with R, I've been doing some correlation matrix by <code>pairwise.complete.obs</code> for my data and I had some variables with <code>NA</code>'s alongs them, which doesn't let me do a <code>findCorrelation</code> from <code>caret</code> to drop variables.</p>
  <p>I do not wish to use <code>na.omit</code> on my dataset, since it does have quite few <code>NA</code>'s and changes or nullifies my pairwise correlation; but omitting my <code>NA</code>'s in the matrix just removes rows, and I need to remove the columns as well to end up with a NxN matrix.</p>
  <p>Is there a function that allows this? So far I cant manage to find one, and maybe I should just do a custom function to retrieve the index of columns with <code>NA</code>'s and do a <code>df[-q,-q]</code> to eliminate them.</p>