On Wed, Jan 7, 2015 at 5:05 PM, Steven Yen <sye...@gmail.com> wrote:
> I like to multiple the first and second column of a 10 x 3 matrix by 100.
> The following did not work. I need this in an operation with a much larger
> scale. Any help?
>
> aa<-matrix(1:30,nrow=10,ncol=3); aa
> bb<-matrix(c(100,100,1),nrow=1,ncol=3); bb
> dim(aa)
> dim(bb)
> aa*bb
>
> Results:
>
> > aa<-matrix(1:30,nrow=10,ncol=3); aa
> [,1] [,2] [,3]
> [1,] 1 11 21
> [2,] 2 12 22
> [3,] 3 13 23
> [4,] 4 14 24
> [5,] 5 15 25
> [6,] 6 16 26
> [7,] 7 17 27
> [8,] 8 18 28
> [9,] 9 19 29
> [10,] 10 20 30
> > bb<-matrix(c(100,100,1),nrow=1,ncol=3); bb
> [,1] [,2] [,3]
> [1,] 100 100 1
> > dim(aa)
> [1] 10 3
> > dim(bb)
> [1] 1 3
> > aa*bb
> Error in aa * bb : non-conformable arrays
>
> >
>
Assuming that this is exactly what you want to do, then
aa[,1:2]<-aa[,1:2]*100;
transcript:
> aa<-matrix(1:30,nrow=10,ncol=3); > aa [,1] [,2] [,3]
[1,] 1 11 21
[2,] 2 12 22
[3,] 3 13 23
[4,] 4 14 24
[5,] 5 15 25
[6,] 6 16 26
[7,] 7 17 27
[8,] 8 18 28
[9,] 9 19 29
[10,] 10 20 30> aa[,1:2]<-aa[,1:2]*100> aa [,1] [,2] [,3]
[1,] 100 1100 21
[2,] 200 1200 22
[3,] 300 1300 23
[4,] 400 1400 24
[5,] 500 1500 25
[6,] 600 1600 26
[7,] 700 1700 27
[8,] 800 1800 28
[9,] 900 1900 29
[10,] 1000 2000 30
>
--
While a transcendent vocabulary is laudable, one must be eternally careful
so that the calculated objective of communication does not become ensconced
in obscurity. In other words, eschew obfuscation.
111,111,111 x 111,111,111 = 12,345,678,987,654,321
Maranatha! <><
John McKown
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