On 12.09.2011 13:16, Raphael Saldanha wrote:
Hi!

Try something like this:

subset(example, disease==TRUE)
subset(example, disease==FALSE)


Hmmm, I think the actual answer to the question is something along this line:

sapply(example[names(example)!="disease"],
       function(x) t.test(x ~ example[["disease"]])[[3]])


Uwe Ligges




On Mon, Sep 12, 2011 at 4:54 AM, C.H.<chainsawti...@gmail.com>  wrote:

Dear R experts,

Suppose I have an data frame likes this:

example<- data.frame(age=c(1,2,3, 4,5,6),
height=c(100,110,120,130,140,150), disease=c(TRUE, TRUE, TRUE, FALSE, FALSE,
FALSE))

example
  age height disease
1   1    100    TRUE
2   2    110    TRUE
3   3    120    TRUE
4   4    130   FALSE
5   5    140   FALSE
6   6    150   FALSE

Is there anyway to compare the age and height between those with
disease=TRUE and disease=FALSE using t.test and extract the p-values
quickly?

I can do this individually

t.test(example$age~example$disease)[3]

But when the number of variable grow to something like 200 it is not
easy any more.

Thanks!

Regards,

CH

--
CH Chan

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