On Nov 11, 2009, at 8:51 PM, zwarren wrote:
Hello!
I'm trying to runs stats on two vars at a time in a big data frame.
I knew
how to do this in SAS many years ago, but have half-forgotten that
as well!
I need, for instance, mean(value) by x-y combination:
x y z value
1 1 1 10
1 1 2 20
1 2 1 30
with results:
x y mean(value)
1 1 15
1 2 30
It's generally a bad idea to incorporate "(" in variable names, but
it's possible:
> aggregate(dat$value, list(dat$x, dat$y), mean)
Group.1 Group.2 x
1 1 1 15
2 1 2 30
> newdat <-aggregate(dat$value, list(dat$x, dat$y), mean)
> names(newdat) <- c("x","y",bquote("mean(value)") )
> newdat
x y mean(value)
1 1 1 15
2 1 2 30
Any help?
Thanks,
~Zack
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