
Hello:
 
Using the built-in dataset aml as an example:
 
data(aml)
If I use instead dummy variables:
 
aml$x1 = (aml$x=="maintained")aml$x2 = (aml$x=="unmaintained")
and I want to plot the survival curve using x1, x2, and I just want the 2 levels, rather than 4 curves from:
 
fit <- survfit(Surv(time, status) ~ x1+x2, data=aml)
plot(fit)
 
I guess because there are 2 levels for each variable?
 
Thanks!
 
p.s. I need to do this more because my dummies are not good to combine and I want to be able to work with them separately also, not becuase I'm crazy!
 
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