Hi,
See ?sweep
For instance, to get your matrix two:
> sweep(a, 2, b, "/")
[,1] [,2]
[1,] 2 24
[2,] 4 28
[3,] 6 32
[4,] 8 36
[5,] 10 40
Sarah
On Mon, Jul 27, 2015 at 4:04 PM, Steven Yen <sye...@gmail.com> wrote:
> I need help with element-by-element division. Below, matrices a and c are
> both 5 x 2 and element-by-element division works as (I) expected. What if
> matrix is 1 by 2: to divide first column of a by b[1] and second column of
> a by b[2]. I had to go around (two ways) to make it work. In Gauss, these
> can be dine by a./b and a./c. Any such simple way in R? Thank!
>
>> a<-matrix(1:10,nrow=5); a
> [,1] [,2]
> [1,] 1 6
> [2,] 2 7
> [3,] 3 8
> [4,] 4 9
> [5,] 5 10
>> b<-matrix(c(0.5,0.25),nrow=1); b
> [,1] [,2]
> [1,] 0.5 0.25
>> c<-matrix(rep(c(0.5,0.25),5),nrow=5,byrow=T); c
> [,1] [,2]
> [1,] 0.5 0.25
> [2,] 0.5 0.25
> [3,] 0.5 0.25
> [4,] 0.5 0.25
> [5,] 0.5 0.25
>
>> one<-a/c; one [,1] [,2]
> [1,] 2 24
> [2,] 4 28
> [3,] 6 32
> [4,] 8 36
> [5,] 10 40
>
>
>> two<-a/b
> Error in a/b : non-conformable arrays
>> two<-cbind(a[,1]/b[1],a[,2]/b[2]); two
> [,1] [,2]
> [1,] 2 24
> [2,] 4 28
> [3,] 6 32
> [4,] 8 36
> [5,] 10 40
>
>> b2<-matrix(rep(b,5),nrow=5,byrow=T); b2 [,1] [,2]
> [1,] 0.5 0.25
> [2,] 0.5 0.25
> [3,] 0.5 0.25
> [4,] 0.5 0.25
> [5,] 0.5 0.25> a/b2 [,1] [,2]
> [1,] 2 24
> [2,] 4 28
> [3,] 6 32
> [4,] 8 36
> [5,] 10 40
--
Sarah Goslee
http://www.functionaldiversity.org
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