How to stop Kaplan-Meier curve at a time point
On Nov 20, 2013, at 12:01 PM, Dr.Vinay Pitchika wrote:
Hello R users I have a question with Kaplan-Meier Curve with respect to my research. We have done a retrospective study on fillings in the tooth and their survival in relation to the many influencing factors. We had a long follow-up time (upto 8yrs for some variables). However, we decided to stop the analysis at the 6year follow up time, so that we can have uniform follow-up time for all the variables. I did play a bit with the formula and tried to stop the Kaplan-Meier curve at my desired time (2190days)or roughly 6 years. However, my question is I want to find the significance (log rank test) at this time point between the two curves; because I am not able to find a way to stop the survfit at this time point with my knowledge. Below is the code I used. Gender2<-survfit(Surv(Survival_days, Outcome)~Gender)
I'm assuming that you have a dataframe with those variables and have attached it. If so, then:
dfrm <- detach(said_df)
# If not, then:
dfrm <- data.frame(Survival_days, Outcome, Gender)
Gender2<-survfit(Surv(Survival_days, Outcome)~Gender,
data=dfrm, subset = Survival_days < 6*365.25 )
plot (Gender2, xmax=2190, mark.time=FALSE, col=c(1:2), xlab="Survival time
(Days)", ylab="Survival probability", main="Gender") # mark.time=FALSE will
remove the censoring lines in the graph. If censoring lines are needed,
then remove the mark.time section in the formula.
legend("topright",c("Females", "Males"), col=(1:2), lwd=0.5)
Am sure, the code in the first line has to be modified. Please help me with
this and I will be very thankful to you.
David Winsemius Alameda, CA, USA