title: Make vector of rows that match a condition in R
body: <p>I have a dataframe 'likes' that looks like this:</p>
  
  <pre><code>uid       Likes
  
  123       Harry Potter
  123       Fitness
  123       Muesli
  123       Fanta
  123       Nokia
  321       Harry Potter
  321       Muesli
  455       Harry Potter
  455       Muesli
  699       Muesli
  123       Belgium
  </code></pre>
  
  <p>Furthermore I have a bunch of strings, for example: <code>WhatLikes &lt;- c("Harry Potter","Muesli")</code></p>
  
  <p>I want a vector of the uid's that 'like' Harry Potter OR Muesli. Take note that <code>WhatLikes</code> is much bigger than this example.</p>
  
  <p>The solution should thus be a vector that contains <code>123</code>,<code>321</code>,<code>455</code>,<code>699</code>.</p>
  
  <p>Help me out! thanks!</p>