title: How to subtract elements from a vector in R?
body: <p>For example, there are two vectors:
  <code>A &lt;- c('H','H','H','M','M','M','L')</code>
  <code>B &lt;- c('H','M','L')</code>
  I would like to subtract B from A, which will produce a new vector like this:<code>C &lt;- c('H','H','M','M')</code>
  I've tried using match(), but it only returned the first index of vector A. Thank you in advance!</p>