# [R] RE : for loops

justin bem justin_bem at yahoo.fr
Wed Apr 25 11:17:14 CEST 2007

```You can see with this simple example.

matrix.t.test<-function(mx){

p<-dim(mx)[2]  #number of column in the matrix
n<-dim(mx)[1]  #number of row

n.tests<- p*(p-1)/2 #Number of tests to be done

tested.var <-rep("",n.tests) #Keep rang of tested
column
r.t.stat<-rep(0, n.tests)#contain t.stat
r.p.val <-rep(0, n.tests)#contain p.values

ctst<-1 #current test
for (i in 1:(p-1)){
for (j in (i+1):p){
r.t.stat[ctst]<-t.test(mx[,i],mx[,j])\$statistic
r.p.val [ctst] <-t.test(mx[,i],mx[,j])\$p.value
tested.var [ctst]<-paste(i,"-",j)
ctst<-ctst+1
}
}

result<-data.frame(tested.var,r.t.stat,r.p.val)
return(result)
}

matrix.t.test(matrix(rnorm(50),nr=10,nc=5))

--- "silvia-montagna at libero.it"
<silvia-montagna at libero.it> a écrit :

> Hello everybody
> I'm very new at using R so probably this is a very
> stupid question.
> I have a matrix of "p" columns and I have to
> calculate for each of them the "two sample
> t-statistic" and p-value and to save the results
> into two different vectors.
> I have divided my matrix into two submatrices:
> submatrix A containing the first "n1" rows (p
> columns) and submatrix B containing the remaining
> "n2" (total rows=n1+n2).
> How can I do this with for loop construction?
> Friendly regards
> Silvia
>
>
>
------------------------------------------------------
> senza canone Telecom
>
> ______________________________________________
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> and provide commented, minimal, self-contained,
> reproducible code.
>

Justin BEM
Elève Ingénieur Statisticien Economiste
BP 294 Yaoundé.
Tél (00237)9597295.

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