[R] t-test

[Rui Barradas]

Hello,

I'm not quite sure I understand, but something like this?

tapply(dat$Score, dat$Name, FUN = mean)
sapply(unique(dat$Name), function(un){
     with(dat, t.test(Score[Name == un], Score[Name != un])$p.value)})

My doubt is in what you mean by "mean for CTK and all". The ?t.test 
gives a confidence interval for the difference in the means, so maybe 
you'll have to look there for what you want.

Hope this helps,

Rui Barradas
Em 04-10-2012 10:34, Nico Met escreveu:
> Dear Group,
>
> I want to do a t-test calculation on a large data set.
>
> I am pasting some part of it
>
> structure(list(Name = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 3L,
> 3L, 3L, 3L, 3L, 3L, 3L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
> 2L), .Label = c("CTK100", "CTK103", "CTK121"), class = "factor"),
>      Score = c(236.9726, 207.0055, 237.3464, 224.4774, 236.5034,
>      206.7382, 233.94, 240.31, 240.9, 235.15, 223.36, 248.67,
>      249.25, 201.4051, 244.1689, 182.2756, 229.001, 241.3211,
>      196.0453, 232.6055, 225.0783, 196.0453, 232.6055, 225.0783
>      )), .Names = c("Name", "Score"), class = "data.frame", row.names =
> c(NA,
> 24L))
>
>
> I want to compare groups with CTK100 and with all the groups and want to
> save the p-values and mean for each of that particular group (for example:
> mean for CTK and all)
> Similarly, for other groups like that CTK121 etc...
>
> Is there any way to automate this process?
>
> Thanks for your advice !!!!!
>
> Nico
>
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>
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