On Jun 20, 2009, at 12:23 AM, j0645073 wrote:
Hello:
So i've fit a hazard function to a set of data using
kmfit<-survfit(Surv(int, event)~factor(cohort))
this factor variable, "cohort" has four levels so naturally the strata
variable has 4 values.
I can use this data to estimate the hazard rate
haz<-n.event/n.risk
That's not valid, but it's close. Try instead:
haz <- kmfit$n.event/kmfit$n.risk
The problem will be to properly categorize the vectors in the survfit
object with your covariate factor, "cohort". (Strata is a somewhat
different term in the language of Cox models.)
and calculate the cumulative hazard function by
H<--log(haz)
Since that is not valid R syntax at all and you say you want
cumulative, then why aren't you summing the hazards?
Now, I would like to plot this cumulative hazard function by time and
differentiate the curves by strata. For the life of me I cannot seem
to do
it.
If you are being asked to do this from scratch and show your work for
homework grading purposes, then by all means, carry on. If not, then
you should be trying:
plot(kmfit, fun="cumhaz")
Any help would be greatly appreciated.
Regards,
j
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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