title: Shapiro test: is.numeric (x) is not TRUE
body: <p>I have problems with the <code>shapiro.test</code> function to check normality. I keep getting the error </p>
  
  <pre><code>is.numeric (x) is not TRUE
  </code></pre>
  
  <p>I use the following dataset (name: <code>Abund2014layer</code>): </p>
  
  <pre><code>Abundance
  0.91567
  0.01256
  ...
  0.85605
  </code></pre>
  
  <p>which goes on for 75 rows.</p>
  
  <p>I implement it as follows:</p>
  
  <pre><code>shapiro.test(Abund2014layer)
  </code></pre>
  
  <p>But I keep getting the error. The input should be a numeric vector of data values, I don't see where it goes wrong.</p>