[R] Using loop for applying function on matrix

[Berend Hasselman]

On 21-05-2013, at 09:16, Suparna Mitra <suparna.mitra.sm at gmail.com> 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) {
> Data=(mdat[,i]*100/x[i], add=T)
> }
> 

See this discussion: http://r.789695.n4.nabble.com/Divide-matrix-columns-by-different-numbers-td4666013.html

Other possibilities taken from that thread

mdat*100/rep(x,each=nrow(mdat))

100*t(t(mdat)/x) 


Berend