" class="external-link">list</a></span><span class="op">(</span></span></span>
<span class="r-in"><span>      formula <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/pkg/survival/man/Surv.html" class="external-link">Surv</a></span><span class="op">(</span><span class="va">U</span>, <span class="va">D</span><span class="op">)</span> <span class="op">~</span> <span class="va">X</span>,</span></span>
<span class="r-in"><span>      method <span class="op">=</span> <span class="st">"breslow"<