R help - Nov 2008 - Strang line while plotting failure curves

Dear R helper,

I encountered a problem when I tried to plot the cumulative failure rate
(i.e. 1 - survival probability). I have used the following code to plot. The
scenario is that patients are randomized to different treatment arm (rev in
the code), the PCI revascularization was monitored over 5 years.

#R code
 testfit <- survfit(Surv(pcifu,pci)~rev,data=subproc)
 testfit$surv <- 1 - testfit$surv
 testfail <- plot(testfit, mark.time=FALSE,col=1:2, main='Failure
Rate')
#End of R code

I arbitarily replaced testfit$surv by computing 1 minus the original
survival rate. So far so good. However, when I plot the manipulated
"testfit", there is a vertical line plotted at x=0, y=0:1. I checked
testfit$time and testfit$surv, nothing weird there. I am very confused where
the vertical line at starting point of time 0 came from. How can I get rid
of it?

Would you pleae help me with this? Thanks a lot!

Jiang

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Lu, Jiang wrote:
> Dear R helper,
> 
> I encountered a problem when I tried to plot the cumulative failure rate
> (i.e. 1 - survival probability). I have used the following code to plot.
The
> scenario is that patients are randomized to different treatment arm (rev in
> the code), the PCI revascularization was monitored over 5 years.
> 
> #R code
>  testfit <- survfit(Surv(pcifu,pci)~rev,data=subproc)
>  testfit$surv <- 1 - testfit$surv
>  testfail <- plot(testfit, mark.time=FALSE,col=1:2, main='Failure
Rate')
> #End of R code
> 
> I arbitarily replaced testfit$surv by computing 1 minus the original
> survival rate. So far so good. However, when I plot the manipulated
> "testfit", there is a vertical line plotted at x=0, y=0:1. I
checked
> testfit$time and testfit$surv, nothing weird there. I am very confused
where
> the vertical line at starting point of time 0 came from. How can I get rid
> of it?
> 
> Would you pleae help me with this? Thanks a lot!
> 
> Jiang
> 
Also see the survplot.* functions in the Design package and their fun 
argument, e.g., fun=function(y)1-y

Frank
> 	[[alternative HTML version deleted]]
> 
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-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University