# [R] A matrix automation problem

Ben Bolker bolker at ufl.edu
Wed Oct 22 15:43:04 CEST 2008

```megh <megh700004 <at> yahoo.com> writes:

>
>
> [I am really sorry if it is double posted, I doubt me previous post could not
> reach forum due to some problem with net]
>
> Suppose I have a matrix :
>
> a = matrix(1:9, 3)
>
> >From this matrix, I construct 9 additional matrices :
>
> i = 1:9
> bi = a * i
>
> Now combining all those 9 new matrices, I construct a final metrix as :
>
> c =
>
> b1 b4 b7
> b2 b5 b8
> b3 b6 b8
>
> I want to automate this procedure for any arbitrary number "i"
>

It may be too specialized, but it sounds like you're looking
for a Kronecker product.

a = matrix(1:9,3)
> kronecker(a,a)
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
[1,]    1    4    7    4   16   28    7   28   49
[2,]    2    5    8    8   20   32   14   35   56
[3,]    3    6    9   12   24   36   21   42   63
[4,]    2    8   14    5   20   35    8   32   56
[5,]    4   10   16   10   25   40   16   40   64
[6,]    6   12   18   15   30   45   24   48   72
[7,]    3   12   21    6   24   42    9   36   63
[8,]    6   15   24   12   30   48   18   45   72
[9,]    9   18   27   18   36   54   27   54   81

Ben Bolker

```