stream fittings. This is made by
      column-binding the vector of 1's with <code>design_obs</code>.</p></dd>

  <dt><code>sv</code></dt>
<dd><p>A matrix of estimated surrogate variables. In simulation
      studies you would probably leave this out and estimate your own
      surrogate variables.</p></dd>

  <dt><code>cormat</code></dt>
<dd><p>A matrix of target correlations between the
      surrogate variables and the permuted variables in the design matrix.
      This might be different from the <code>