s="op">)</span></span>
<span><span class="va">dat</span> <span class="op">&lt;-</span> <span class="va">data.read</span></span>
<span></span>
<span><span class="co">#------ Definition of item response functions</span></span>
<span><span class="co">#*** IRF 2PL</span></span>
<span><span class="va">P_2PL</span> <span class="op">&lt;-</span> <span class="kw">function</span><span class="op">(</span> <span class="va">par</span>, <span class="va">Theta</span>, <span class="va">ncat</span><span class="op">)</span>