R help - Mar 2008 - survival curve for only certain values of a factor

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!
 
_________________________________________________________________
Create a handy button so your friends can add U to their buddy list. Try it now!

	[[alternative HTML version deleted]]

Chang Liu <changisme <at> hotmail.com> writes:
> 
> 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:

I don's understand what you want, but the first step is definitively
incorrect
apart from the missint line break. The levels of aml are

"Maintained","Nonmaintained"

so both your "==" lead to all-false levels.

Dieter