title: Extract sample variance from svykm (survey package by Lumley) for complex survey analysis
body: <p>In order to compare two survival curves at a fixed point in time and perform basically a two sample test, I need to extract the sample variance of the estimate at a given point in time.</p>
  <p>For an object created with the svykm function from Thomas Lumley's survey package in R, this should be accessible in the varlog list. Do the entries in this list constitute the transformed variances on the log scale or the untransformed variances?</p>
  <p>I have read the <a href="https://www.rdocumentation.org/packages/survey/versions/4.0/topics/svykm" rel="nofollow noreferrer">documentation</a> provided for the survey package, but did not fully come to a conclusion. I note that confidence intervals are computed on the log(survival) scale, following the default in survival package and their bounds are given as <code>exp(log(x$surv)+1.96*sqrt(x$varlog))</code> and <code>exp(log(x$surv)-1.96*sqrt(x$varlog))</code> in the <a href="https://rdrr.io/rforge/survey/src/R/svykm.R" rel="nofollow noreferrer">R package documentation</a>.</p>