R predict.cox function type expected

Question

I am using cox model for prediction.

fit <- coxph(Surv(time, status) ~ age + ph.ecog + strata(inst), lung)
predict(fit,type="expected")

In the predict.coxph doc, it says type expected is 'the expected number of events given the covariates and follow-up time'. What is the follow-up time means here? How can I change it?

In the case presented with no newdata argument, the followup time is simply the `time` variable. — IRTFM, Jun 30 '15 at 15:36
Thanks, if I want to predict for new data how can I change the time? — Yoki, Jun 30 '15 at 15:57

IRTFM · Accepted Answer · 2015-07-10T15:56:32.310

This is an example of the "expected" for one particular set of patient features with a single time chosen to be greater than the mean survival time for this cohort, but using all the unique institution codes for the 'lung' dataset.

 (pr.fit.new <- predict(fit, newdata=data.frame(age=50, time=365, status=0, 
                                ph.ecog=2,inst=unique(lung$inst[!is.na(lung$inst)]) ),
                        type="expected"))
 [1] 1.1886094 1.7679429 1.6651195 1.3117278 0.7743925 0.8501810
 [7] 1.9686954 1.2560981 2.5845069 0.6513932 1.1241870 1.1515346
[13] 1.1616482 1.9071766 4.2468797 0.4921904 0.5875339 0.5647238

The strata have remarkably different "baseline hazards" which produces material differences in the "expected" for hypothetical persons with the same covariate and period of observation.

R predict.cox function type expected

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