On Sep 15, 2010, at 7:40 PM, Dennis Murphy wrote:
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.
The two-column matrix indexing strategy is one of those truly powerful
devices in R. Thanks for reminding us of it, Dennis. It would allow
one even more complex operations such as taking the "same section" of
two matrices and add or multiplying. I had composed a clunky rbind/
cbind approach, but threw it away when I saw this one.
Note to self: It's also a powerful lookup strategy into tables.
--
David
HTH,
Dennis
On Wed, Sep 15, 2010 at 4:31 PM, Nicolas Gutierrez <nicol...@uw.edu>
wrote:
Hi All,
Im 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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______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
