# [R] Using loop for applying function on matrix

Pascal Oettli kridox at ymail.com
Tue May 21 11:27:53 CEST 2013

```Hello,

If you *really* need a loop:

Data <- array(NA, dim(mdat))
for(i in 1:ncol(mdat)){
Data[,i] <- mdat[,i]*100/x[i]
}

But I would consider first the thread cited by Berend.

Regards,
Pascal

On 05/21/2013 06:19 PM, Suparna Mitra wrote:
>    I am presently using it with sweep. But here in the question I just
> gave one simple example. In reality I need several functions to run.
> Thus I was wondering, if without sweep, I can use loop. Also want to
> learn how to do this using loop.
> Any help will be really great,
> Thanks,
> Mitra
>
> Dr. Suparna Mitra
> Department of Molecular and Clinical Pharmacology
> Institute of Translational Medicine University of Liverpool
> Block A: Waterhouse Buildings
> 1-5 Brownlow Street
> Liverpool
> L69 3GL
>
> Tel.  +44 (0)151 795 5414
> M: +44 (0) 7523228621
> Internal ext: 55401
>
>
>
> On 21 May 2013 16:29, Pascal Oettli <kridox at ymail.com
> <mailto:kridox at ymail.com>> wrote:
>
>     Hi,
>
>     ?sweep
>
>     mdat <-
>     matrix(c(1,11,2,10,5,2,12,3,9,__6,3,13,4,8,7,4,10,5,9,8,5,10,__6,10,4),5,5)
>     x <- c(14,15,10,11,18)
>
>     sweep(mdat*100, 2, x, FUN='/')
>
>                [,1]     [,2] [,3]     [,4]     [,5]
>     [1,]  7.142857 13.33333   30 36.36364 27.77778
>     [2,] 78.571429 80.00000  130 90.90909 55.55556
>     [3,] 14.285714 20.00000   40 45.45455 33.33333
>     [4,] 71.428571 60.00000   80 81.81818 55.55556
>     [5,] 35.714286 40.00000   70 72.72727 22.22222
>
>     Hope this helps,
>     Pascal
>
>
>
>     On 05/21/2013 04:16 PM, Suparna Mitra wrote:
>
>         Hello R Experts,
>             I need a bit of help in using loop.
>         I have a matrix onto which I need to use several functions.
>
>         In a simplified form suppose my matrix is
>
>             mdat
>
>                [,1] [,2] [,3] [,4] [,5]
>         [1,]    1    2    3    4    5
>         [2,]   11   12   13   10   10
>         [3,]    2    3    4    5    6
>         [4,]   10    9    8    9   10
>         [5,]    5    6    7    8    4
>
>         And I have one vector
>
>             x
>
>         [1] 14 15 10 11 18
>
>         Now suppose in simple form I want to create a matrix in which
>         each col
>         value will be divided with consecutive no from vector x. For example
>
>         column 1 of new vector will be C1=mdat[,1]*100/x[1]
>
>             C1
>
>         [1]  7.142857 78.571429 14.285714 71.428571 35.714286
>
>         Now how can I use the loop to have the complete vector at a time?
>         I tried something like this, but in vain.
>         for(i in 1:5) {
>         }
>
>         Any help will be really great.
>         Thanks,
>         Mitra
>
>                  [[alternative HTML version deleted]]
>
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>

```