Hi:

Try something like this:

ind <- as.matrix(expand.grid(rownames(U), colnames(U)))
Uempty[ind] <- U[ind]

ind should be a two column matrix of (row, col) indices. Then just replace
the values of Uempty associated with those indices with the corresponding
entries of U.

HTH,
Dennis

On Wed, Sep 15, 2010 at 4:31 PM, Nicolas Gutierrez <nicolasg@uw.edu> wrote:

> Hi All,
>
> I’m trying to superimpose (or "add")  two matrices:
>
> 1. resulting from a table function with frequencies:
>
> > U=table(pop$xloc, pop$yloc))
>
>      14 15 16 17 18 19 20 21 22
>  5   0  0  0  0  0  0  0  0  0
>  7   0  0  0  0  0  0  0  0  0
>  8   0  0  0  0  0  0  0  0  0
>  9   0  0  0  0  0  0  9  0  5
>  10  0  0  0  0  0  0  0  0  0
>  11  0  0  0  0  0  0  0  0  0
>
> 2. The second created to match my spatial grid (20x25):
>
> > Uempty=matrix(data = 0, nrow = 20, ncol = 25)
>
> I want to place each element of U (e.g. U[22,9]=5) in the corresponding
> cell of Uempty and end up with this final matrix like this:
>
>      1  2  3 ...  22 23 24 25
>  5   0  0  0  ...  0  0  0  0
>  :   :  :  :  ...  :  :  :  :
>  7   0  0  0  ...  0  0  0  0
>  8   0  0  0  ...  0  0  0  0
>  9   0  0  0  ...  5  0  0  0
>  :   :  :  :  ...  :  :  :  :
>  20  0  0  0  ...  0  0  0  0
>
> Any ideas?
>
> Thanks!!!
>
> Nico
>
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