s="ref-description">
    <p>This function implements a structured latent class model for
polytomous item responses (Formann, 1985, 1992). Lasso estimation for the
item parameters is included (Chen, Liu, Xu &amp; Ying, 2015;
Chen, Li, Liu &amp; Ying, 2017; Sun, Chen, Liu, Ying &amp; Xin,  2016).</p>
    </div>

    <div id="ref-usage">
    <div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">slca</span><span class="op">(</span><span class="va">data</span>, group<span class="op">=</s