R help - Jul 2009 - Passing arguments to with()

Hi,

I've been wondering how to write a function that will produce results
from multiple tests (eg. paired t-tests) for all or several variables
in some data frame. I'd like it to do t-test for each variable ('x')
in 'data' by 'y'. I'm stuck in here:

function(data,y) {
for (x in names(data)) {
	with(data, t.test(x~y))
}}

How to tell 'with' that 'x' and 'y' are names of columns
in 'data'? Or
pass similar arguments?

I probably understand the logic why this is not working, but still
don't know how to make it work.

Thanks in advance for any help!
Timo

On 08/07/2009 10:01 AM, Tymek Wo?odz'ko wrote:
> Hi,
> 
> I've been wondering how to write a function that will produce results
> from multiple tests (eg. paired t-tests) for all or several variables
> in some data frame. I'd like it to do t-test for each variable
('x')
> in 'data' by 'y'. I'm stuck in here:
> 
> function(data,y) {
> for (x in names(data)) {
> 	with(data, t.test(x~y))
> }}
> 
> How to tell 'with' that 'x' and 'y' are names of
columns in 'data'? Or
> pass similar arguments?
Don't use with.  Use t.test(data[[x]] ~ data[[y]]).

Duncan Murdoch
> 
> I probably understand the logic why this is not working, but still
> don't know how to make it work.
> 
> Thanks in advance for any help!
> Timo
> 
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