R help - Oct 2007 - Looped t.test results according to a subset variable

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

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
> 
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