title: Do I always have to unlist a dataframe/tibble before taking a column mean?
body: <p>I wanted to use a pipe to take a mean of a column from some data in a package, and was surprised when I could not. </p>
  
  <p>At first I thought it had to do with piping, but apparently it was because the df column needed to be unlisted before taking the mean. Is it possible to pipe data from a df/tibble directly to a mean function without de-listing first?</p>
  
  <pre><code>install.packages("UsingR")
  library(UsingR)
  library(dplyr)
  
  father.son %&gt;% 
    filter(round(fheight) == 71) %&gt;%
    select(sheight) %&gt;% mean
  
  [1] NA
  Warning message:
  In mean.default(.) : argument is not numeric or logical: returning NA
  </code></pre>
  
  <p>When I pipe all that into a new object and unlist it, I can take the mean; can I do that right from the pipe?</p>
  
  <pre><code>s &lt;- father.son %&gt;% 
    filter(round(fheight) == 71) %&gt;%
    select(sheight)
  mean(unlist(s))
  
  &gt; mean(unlist(s))
  [1] 70.54082
  </code></pre>