 object function like <code>objectfun = "multi:softmax"</code> and how to evaluate (e.g. <code>evalmetric = "merror"</code>). Also, you can specify the range of xgboost options like eta (<code>eta_range</code>) and subsample (<code>subsample_range</code>).</p>
<p>In only <code><a href="../reference/xgb_cv_opt.html">xgb_cv_opt()</a></code> function, the returned value means the value you specified in <code>evalmetric</code> option, so when you specify the evaluation metric “merror” or “(m)logloss”, t