title: Number at risk table using survplot with cph() object
body: <p>This is pretty specific to the rms package. When using survplot with a cph object, the number at risk table is not stratified according to the covariate. using npsurv() does this correctly.</p>
  
  <pre><code>library(survival);library(rms)
  data(lung)
  fit &lt;- cph(Surv(time, status==2) ~ sex,data = lung,surv = TRUE,x=TRUE, y=TRUE)
  survplot(fit, n.risk=TRUE)
  # compared to:
   survplot(npsurv(fit$sformula, data = lung), conf= "none",n.risk=TRUE)
  </code></pre>
  
  <p>For usual use cases I guess re-running the model with npsurv will do, but for others, like when wanting to use fit.mult.impute (my specific use case), you want to use the "original" fit created by cph().
  Is there a work-around/way to fix this?</p>