lass="anchor" aria-label="anchor" href="#value"></a></h2>
    <p>vector of variable names</p>
    </div>

    <div class="section level2">
    <h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="va">ff</span> <span class="op">&lt;-</span> <span class="va">yvar</span> <span class="op">~</span> <span class="va">x1</span> <span class="op">+</span> <span class="va">x2<