title: Using table() in dplyr chain
body: <p>Can someone explain why <code>table()</code>doesn't work inside a chain of dplyr-magrittr piped operations? Here's a simple reprex:   </p>
  
  <pre><code>tibble(
    type = c("Fast", "Slow", "Fast", "Fast", "Slow"),
    colour = c("Blue", "Blue", "Red", "Red", "Red")
  ) %&gt;% table(.$type, .$colour)
  </code></pre>
  
  <blockquote>
    <p>Error in sort.list(y) : 'x' must be atomic for 'sort.list'
        Have you called 'sort' on a list?</p>
  </blockquote>
  
  <p>But this works of course: </p>
  
  <pre><code>df &lt;- tibble(
    type = c("Fast", "Slow", "Fast", "Fast", "Slow"),
    colour = c("Blue", "Blue", "Red", "Red", "Red")
  ) 
  
  table(df$type, df$colour)
  
  
         Blue Red
    Fast    1   2
    Slow    1   1
  </code></pre>