# [R] elegant matrix creation

Spencer Graves spencer.graves at pdf.com
Wed Jul 28 16:34:00 CEST 2004

```      It's not obvious what pattern you want, but some variants of the
following would work for jj1 and jj2:

1+outer(1:9, 1:9, "+")%%3

In particular the following are equal to your jj1 and jj2:

jj1. <- 1+outer(0:8, rep(0:2, e=3), "+")%%3

jj2. <- 1+outer(0:8, c(1,2,1,3,1,3,2,3,2)-1, "+")%%3

I couldn't figure out jj3, but this system may not work so easily
for that.  hope this helps.  spencer graves

Robin Hankin wrote:

>Hello everybody.
>
>I am trying to reproduce a particular matrix in an elegant way.  If I
>have
>
>jj1 <-
>structure(c(1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,2,
>3,1,2,3,1,2,3,1,2,3,2,3,1,2,3,1,2,3,1,2,3,
>1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,3,1,2,3,1,
>2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,
>2),.Dim = as.integer(c(9,9)))
>
>[ image(jj1) is good here ] then I can get this with
>
>kronecker(matrix(1,3,1),kronecker(1+outer(0:2,0:2,"+")%%3,matrix(1,1,3)))
>
>I want to reproduce the following matrices in an equivalent way:
>
>jj2 <- matrix(c(1,2,3,1,2,3,1,2,3,2,3,1,2,3,1,2,3,1,
>1,2,3,1,2,3,1,2,3,3,1,2,3,1,2,3,1,2,1,2,3,1,2,
>3,1,2,3,3,1,2,3,1,2,3,1,2,2,3,1,2,3,1,2,3,1,3,
>1,2,3,1,2,3,1,2,2,3,1,2,3,1,2,3,1),9,9)
>
>jj3 <- structure(c(1,2,3,2,3,1,3,1,2,1,2,1,2,3,2,3,1,
>3,1,3,1,2,1,2,3,2,3,2,3,1,3,1,2,1,2,3,2,3,
>2,3,1,3,1,2,1,2,1,2,3,2,3,1,3,1,3,1,2,1,2,
>3,2,3,1,3,1,3,1,2,1,2,3,2,3,2,3,1,3,1,2,1, 2),.Dim =
>as.integer(c(9,9)))
>
>[ note that jj1-jj3 each have precisely 3 occurrences of A, B, and C
>along each row, column and (broken) diagonal ].
>
>Can anyone give me a nice elegant way of creating jj2 and jj3 please?
>
>
>

```