title: How to select non-numeric columns using dplyr::select_if
body: <p>I need to select all columns that are not numeric. I can select all numeric columns easily using <code>select_if</code>:</p>
  
  <pre><code>mtcars %&gt;% select_if(is.numeric)
  </code></pre>
  
  <p>What if I want to select <code>non-numeric</code> columns? I tried:</p>
  
  <pre><code>mtcars %&gt;% select_if(!is.numeric)
  </code></pre>
  
  <p>But I got error message below:</p>
  
  <pre><code>Error in !is.numeric : invalid argument type
  </code></pre>
  
  <p>Thanks a lot for help!</p>