  <div id="value">
    <h2>Value</h2>
    <p><code>P</code> A \(n\) by \(n\) symmetric positive definite
    matrix.</p>
<p><code>Z</code> A \(n\) by \(p\) matrix with orthonormal rows.</p>
<p>Note that <code>X == P %*% Z</code>, up to numerical precision.</p>
    </div>
    <div id="details">
    <h2>Details</h2>
    <p><code>polar</code> Takes a matrix \(X\), of dimensions \(n\) by
\(p\), and returns two matrices \(P\) and \(Z\) such that
\(X = PZ\). \(P\) is a symmetric positive definite matrix of
dimens