title: type numeric not supported by autoplot
body: <p>I've seen other errors of objects not supported by autoplot but not of type numeric.
  <a href="https://stackoverflow.com/questions/30056144/r-ggfortify-objects-of-type-prcomp-not-supported-by-autoplot">example1</a>
  <a href="https://stackoverflow.com/questions/41165401/error-objects-of-type-lm-not-supported-by-autoplot">example2</a></p>
  
  <p>Say I create some random numbers</p>
  
  <pre><code>require(ggfortify)
  require(ggplot2)
  </code></pre>
  
  <p><code>data &lt;- c(.034,0343,0343,.0653,.034,0343,0343,.0653)</code></p>
  
  <pre><code>autoplot(data)
  
  Error: Objects of type numeric not supported by autoplot.
  </code></pre>
  
  <p>I would appreciate any help!</p>