# [R] t-test

arun smartpink111 at yahoo.com
Thu Oct 4 14:31:55 CEST 2012

```HI,
Try this:
sapply(split(dat,dat\$Name),function(x) t.test(x[,2],dat[,2])\$p.value)
#    CTK100     CTK103     CTK121
#0.86330310 0.32706859 0.02023357
A.K.

----- Original Message -----
From: Nico Met <nicomet80 at gmail.com>
Cc: r-help at r-project.org; r-help <r-help at stat.math.ethz.ch>
Sent: Thursday, October 4, 2012 6:37 AM
Subject: Re: [R] t-test

Dear Rui,

Many thanks for help.

"mean for CTK and all"  = comparison between mean of all groups ( which
means second col) vs. each groups like CTK100, CTK121 etc.

Regards

Nico

On Thu, Oct 4, 2012 at 12:28 PM, Rui Barradas <ruipbarradas at sapo.pt> wrote:

> 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,
>
> 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?
>>
>>
>> Nico
>>
>>         [[alternative HTML version deleted]]
>>
>> ______________________________**________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
>> posting-guide.html <http://www.R-project.org/posting-guide.html>
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>

[[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help