[R] Looped t.test results according to a subset variable

[jim holtman]

I think what you want to write is:

by(your.df, quiz, function(.sub){
    t.test(percent ~ group, data=.sub)
}


On 10/22/07, Matthew Dubins <matt.dubins at utoronto.ca> wrote:
> I've tried to use by(), but the closest i got to it doing what I wanted
> was using the following:
>
>  by(percent, quiz, function(percent) {t.test(percent~group,
> data=marks.long)})
>
> But the results it gave me weren't t.tests of percent by group according
> to quiz number.
>
>
> Julian Burgos wrote:
> > See by()
> >
> > Matthew Dubins wrote:
> >> Hi all,
> >>
> >> I wrote a simple function that gives me multiple t.test results
> >> according to a subset variable and am wondering whether or not I
> >> reinvented the wheel.  Observe:
> >>
> >> t.test.sub <- function (formula, data, sub, ...)
> >>     {
> >>         for(i in 1:max(sub))
> >>             {
> >>                 print(t.test(formula, data = subset(data, sub == i),
> >> ...))
> >>             }
> >>     }
> >>
> >> Is there already a similar function in some package?
> >>
> >> Thanks,
> >> Matthew Dubins
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
> >> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?