title: Calculate Mean of Comma-Separated String of Numbers
body: <p>I have a column in my dataframe that is made up of strings of numbers, separated by commas. I would like to convert the string to a list of numbers, and then get the mean. My dataframe, <code>df</code>:</p>
  
  <pre><code>a3
  1,5,2
  103.1
  34,6
  </code></pre>
  
  <p>First, I converted the string to a list:</p>
  
  <pre><code>&gt; df$a3_list &lt;- strsplit(as.character(df$a3), split = ',')
  </code></pre>
  
  <p>New <code>df</code>:</p>
  
  <pre><code>a3    a3_list
  1,5,2 c("1", "5", "2")
  103.1 103.1
  34,6  c("34", "6")
  </code></pre>
  
  <p>At this point, however, I'm not sure how to get a new column containing the mean of each cell in <code>df$a3_list</code></p>