vectors containing the least-squares
  estimates of the coefficients (<code>betahat</code>) and their standard
  errors (<code>sebetahat</code>). Optionally, and only when a matrix of
  covariates <code>Z</code> is provided, a third vector <code>residuals</code>  containing the residuals is returned.</p>
    </div>

    <div id="ref-examples">
    <h2>Examples</h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span class="fu"><a href="https://rdrr.io/r/base/Random.html" cla