[R] Calculating the t-test for each row

[John Kane]

If I understand you correctly what you want to do is
do t-test (mu=0) for each column of the data. 

Treating the data as a data.frame rather than a matrix
you can do something like this and then pick out the
p-values but with 140 t-tests I don't know what you'll
get in terms of anything meaninful.  

======================================================


aa <- data.frame(a=rnorm(25, 5, 2), b=rnorm(1:25,
0,1))
mytea <- apply(aa, 2, t.test)

tresults <- lapply(mytea, function(.tres) {      
 
data.frame(t.value=.tres[1],dfs=.tres[2],conf.int1=.tres$conf.int[1],conf.int2=
 .tres$conf.int[2],p.value=.tres[3])
      })

finalresults <- do.call(rbind, tresults) 

=====================================================
(Thanks to Mark Leeds for the lapply approach)


--- Keizer_71 <christophe.lo at gmail.com> wrote:

> 
> Hi Everyone,
> 
> I need some simple help.
> 
> Here are my codes
> 
> ##########will give me 10000
> probesets####################
> data.sub =
>
data.matrix[order(variableprobe,decreasing=TRUE),][1:10000,]
> dim(data.sub)
> data_output<-write.table(data.sub, file =
> "c://data_output.csv", sep = ",",
> col.names = NA) 
> 
> When i export to excel, it shows me this. This is
> just a short version.
> There are 1000 rows and 140 columns
> 
> 	Sample_1_D	Sample_1_C	Sample_2_D	Sample_2_C
> 1	2.425509867	11.34031409	11.46868531	11.75741478
> 
> 
> Here is my question: How do create a new row and
> calculate the t-test so
> that it will give me the p-value
> 
> Here is what i am looking for. The p-value is not
> correct but just an
> example. It needs to calculate the entire each row.
> There are 10000 rows and
> 140 columns.
> 
> thanks
> Kei
> 
> 	Sample_1_D	Sample_1_C	Sample_2_D	Sample_2_C   
> p-value
> 1	2.425509867	11.34031409	11.46868531	11.75741478   
>  .00341111
> 
> I tried something like this.
> 
> t.test(data.sub,mu=0)
> 
> I am pretty new to R. I think it is showing me the
> entire p-value.
> 
> 
> 
> -- 
> View this message in context:
>
http://www.nabble.com/Calculating-the-t-test-for-each-row-tp15808716p15808716.html
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> Nabble.com.
> 
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