title: Regular expressions (RegEx) and dplyr::filter()
body: <p>I have a simple data frame that looks like this:</p>
  
  <pre><code>x &lt;- c("aa", "aa", "aa", "bb", "cc", "cc", "cc")
  y &lt;- c(101, 102, 113, 201, 202, 344, 407)
  df = data.frame(x, y)    
  
      x   y
  1   aa  101
  2   aa  102
  3   aa  113
  4   bb  201
  5   cc  202
  6   cc  344
  7   cc  407
  </code></pre>
  
  <p>I would like to use a dplyr::filter() and a RegEx to filter out all the <code>y</code> observations that start with the number <code>1</code></p>
  
  <p>I'm imagining that the code will look something like this:</p>
  
  <pre><code>df %&gt;%
    filter(y != grep("^1")) 
  </code></pre>
  
  <p>But I am getting an <code>Error in grep("^1") : argument "x" is missing, with no default</code></p>