# [R] Working with Matrix

Fri Jan 4 14:08:35 CET 2013

```Hello,

Using part of your code, it's possible to do without Reduce, have foo
(fun, below) do the job.

fun <- function(x, y, FUN = `+`){
if(nrow(x) < nrow(y)){
nas <- matrix(NA, ncol = ncol(x), nrow = nrow(y) - nrow(x))
x <- rbind(x, nas)
}else{
nas <- matrix(NA, ncol = ncol(y), nrow = nrow(x) - nrow(y))
y <- rbind(y, nas)
}
FUN(x, y)
}

fun(Mat1, Mat2)
fun(Mat1, Mat2, `*`)  # Note the back quotes

Hope this helps,

Em 04-01-2013 12:06, Jorge I Velez escreveu:
> Dear Christofer,
>
> You can try the following:
>
> # proccess the matrices
> foo <- function(m1, m2){
>   if(ncol(m1) != ncol(m2)) stop('number of columns should be equal')
>   if(nrow(m1) < nrow(m2)){
> nas <- matrix(NA, ncol = ncol(m1), nrow = nrow(m2) - nrow(m1))
>   m1 <- rbind(m1, nas)
> }
> else{
>   nas <- matrix(NA, ncol = ncol(m1), nrow = nrow(m1) - nrow(m2))
> m2 <- rbind(m2, nas)
>   }
>   list(m1, m2)
> }
>
> # process
> r <- foo(Mat1, Mat2)
>
> # basic operations
> Reduce("+", r)
> Reduce("*", r)
> Reduce("/", r)
> Reduce("-", r)
>
> HTH,
> Jorge.-
>
>
> On Fri, Jan 4, 2013 at 10:47 PM, Christofer Bogaso <> wrote:
>
>> Hello again,
>>
>> Let say I have 2 matrices which equal number of columns but different
>> number of rows like:
>>
>> Mat1 <- matrix(1:20, 4, 5)
>> Mat2 <- matrix(1:25, 5, 5)
>>
>> Now for each column 1-to-5 I need to fetch the corresponding columns
>> of these 2 matrices and add the corresponding elements (ignoring NA
>> values if any). Therefore for the 1st column I need to do:
>>
>> (1+1), (2+2),...,(4+4), (NA+5)
>>
>> and so on
>>
>> And the resulting numbers will be stored in some other matrix
>>
>> Also note that, here I gave the example of addition, however, this can
>> be any user defined function.
>>
>> Is there any R way to do that, without using any for-loop?
>>
>> Thanks and regards,
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
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>
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