gth as <code>Y</code>; if sample-splitting
is desired, then the value of <code>f2</code> at each position should be the result
of predicting from a model trained without that observation.</p></dd>


<dt>indx</dt>
<dd><p>the indices of the covariate(s) to calculate variable
importance for; defaults to 1.</p></dd>


<dt>type</dt>
<dd><p>the type of importance to compute; defaults to
<code>r_squared</code>, but other supported options are <code>auc</code>,
<code>accuracy</code>, <code>deviance</code>, and <cod