[R] How to create arbitrary number of loops in R

[ilai]

On Thu, Mar 29, 2012 at 9:27 AM, ilai <keren at math.montana.edu> wrote:

Oops, sent to fast. A (maybe) clearer solution:

 f <- function(x,m){
cmway <- combn(ncol(x),m)
xx <- x[,cmway]
dim(xx) <- c(nrow(x),nrow(cmway),ncol(cmway))
xx
}

f(M,3)
str(sapply(2:4,f,x=M))

And again lapply / apply , or even return icc(xx) in f

Cheers

> To cbind, you don't need a loop
>
> (M <- matrix(1:50,nc=10))
> c2way <- combn(ncol(M),2)
> MM <- M[,c2way]
> dim(MM) <- c(nrow(M),nrow(c2way),ncol(c2way))
> MM
>
> c3way <- combn(ncol(M),3)
> MMM <- M[,c3way]
> dim(MMM) <- c(nrow(M),nrow(c3way),ncol(c3way))
> MMM
>
> etc. etc.
>
> Than you can (untested for icc) loop your function as in
> apply(MMM,3,somefun)
>
> cheers
>
> On Thu, Mar 29, 2012 at 7:28 AM, Dai, Hongying, <hdai at cmh.edu> wrote:
>> Dear R users,
>>
>> I'm wondering how I can generate an arbitrary number of loops in R.
>> For instance, I can generate two "for" loops to get ICC among any two-way combination among 10 variables. Here is the code
>>
>> n<-10
>> for (i in 1:(n-1))
>> {
>> for (j in (i+1):n)
>> {
>> icc(cbind(DATA[,i],DATA[,j]))
>> }
>> }
>> If I need three-way combination, then a code with three "for" loops will be:
>> n<-10
>> for (i in 1:(n-2))
>> {
>> for (j in (i+1):(n-1))
>> {
>> for (k in (j+1):n)
>> {
>> icc(cbind(DATA[,i],DATA[,j],DATA[,k]))
>> }
>> }
>> }
>> But how can I write a code if I need all m=2, 3, 4,... loops for arbitrary m-way combinations?
>> Thanks!
>> Daisy
>>
>>
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