title: R calculating mean of a column
body: <p>I want to calculate mean of a column in R. The column is written in a csv file, namely datafile, as follows.</p>
  
  <pre><code>X
  12
  14
  10
  ...
  </code></pre>
  
  <p>I read the data as follows.</p>
  
  <pre><code>myData &lt;- read.csv("datafile.csv")
  </code></pre>
  
  <p>When I want to calculate the mean as <code>mean(myData)</code>, I get the following message:</p>
  
  <pre><code>[1] NA Warning message: In mean.default(myData) : argument is not numeric or logical: returning NA
  </code></pre>