le.</p>
<p>If a character vector is supplied in the <code>adjust_vars</code> argument, the Kaplan-Meier estimates are created for each combination of all supplied variables. If the sample size is small and/or there are many levels in these variables, the estimates can become unstable or undefined. Because it is a weighted average of Kaplan-Meier curves, estimates for this method are only defined for points in time with a valied Kaplan-Meier estimate in all strata. Continuing the example from above, if the K