[R] "pattern matching" accross multiple matrices

[jim holtman]

You are putting your results back into "A" which might change things
as you execute.  This might be a faster way:

result <- matrix(NA,dim(A)[1], dim(A)[2])

# now compute the cases
result[(A ==1) & (D == 1) & (P ==1)] <- Case1
result[(A == -1) & (D == -1) & (P == -1)] <- Case2
.......

On Nov 8, 2007 12:27 PM, Martin Tomko <martin.tomko at gmail.com> wrote:
> Hi all,
>
> I have a set of patterns which can occur in a series of (3) matrices. I
> want to identify those and create a fourth one with the identifiers of
> the cases.
>
> Something like:
>
>        for (i in 1:l) {
>                for (j in 1:w) {
>
>                A[A[i,j]==1 & D[i,j]==1 & P[i,j]==1] <- Case1;
>                A[A[i,j]==-1 & D[i,j]==-1 & P[i,j]==-1] <- Case2;
>
> etc....
> }
> }
>
> the code seems to run, but is very slow.... Could anyone please suggest
> a better approach? I was thinking that 3 matrices could be stacked in a
> cube, and the column of a cube searched for a pattern, but am not sure
> how to do that...
>
> Thanks
> Martin
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?