ass="op">~</span> <span class="va">disp</span> <span class="op">+</span> <span class="fu"><a href="https://rdrr.io/r/base/factor.html" class="external-link">as.factor</a></span><span class="op">(</span><span class="va">am</span><span class="op">)</span><span class="op">*</span><span class="fu"><a href="https://rdrr.io/r/base/factor.html" class="external-link">as.factor</a></span><span class="op">(</span><span class="va">vs</span><span class="op">)</span>, data <span class="op">=</span> <span class="va">mtca