title: RDA, Error in colMeans(x, na.rm = TRUE) : 'x' must be numeric, when data is numeric?
body: <p>I want to perform a rda in R, using vegan.</p>
  
  <p>My code looks like this:</p>
  
  <pre><code>species&lt;- read.delim("springspecies1.txt", header=T)
  envdata&lt;- read.delim("springenv1.txt", header=T)
  
  RDA &lt;- rda(species~Temperature + Salinity + O2 + Phosphate + Nitrate + Silica, envdata, scale=T, na.action=na.omit)
  </code></pre>
  
  <p>and I get the error message:</p>
  
  <pre><code>Error in colMeans(x, na.rm = TRUE) : 'x' must be numeric
  </code></pre>
  
  <p>when I check my data I get:</p>
  
  <pre><code>sapply(species, mode)
        Station          Year         Month     S.marinoi      C.tripos 
      "numeric"     "numeric"     "numeric"     "numeric"     "numeric" 
        P.alata     P.seriata    R.setigera    C.pelagica D.confervacea 
      "numeric"     "numeric"     "numeric"     "numeric"     "numeric" 
    C.decipiens    P.farcimen       C.furca 
      "numeric"     "numeric"     "numeric"
  </code></pre>
  
  <p>There are no NA or blanks in my data set. But it seems that the species data set is the problem. I compiled a new data set with the species, but I get the same problem again. Any ideas?</p>