terms</code> should take the form
  <code>spp1 + spp2 + spp3</code>.</p>
<p>The default is to fit a predictive CoCA model using SIMPLS via a
  modified version of <code><a href='https://rdrr.io/pkg/pls/man/simpls.fit.html'>simpls.fit</a></code> from package
  <code>pls</code>. Alternatively, <code>reg.method = "eigen"</code> fits the model
  using an older, slower eigen analysis version of the SIMPLS
  algorithm. <code>reg.method = "eigen"</code> is about 100% slower than
  <code>reg.method = "simpls"</code