How to apply a function to all elements with the same indices in multiple arrays? E.g.:
I have two spatial grids defined the same way (i.e., same number of rows and columns--and dimensions, both 2D). Wherever both * the value of an element i,j in the first grid is NA * the value of element i,j in the second grid is !NA I want to copy the value from grid2[i,j] to grid1[i,j]. These matrices are not too big, so I'm able to do this with loops, but I know that's not "the R way." How to parallelize/vectorize this, e.g., with a single call to an 'apply'-type method? I believe I know how to operate on a single matrix (e.g., by using `apply` to traverse it by rows or cols), but not how to operate on multiple matrices. Extra points for solutions that generalize to 3D or 4D (i.e., that allow applying the same function to identical elements in n arrays of n dimensions), since I will almost certainly need to work on arrays of those dimensions eventually. Apologies if this is a FAQ, but a fair amount of googling via rseek.org is not finding an answer (perhaps because I'm not using the correct search terms). Feel free (in fact, be encouraged :-) to reply directly to me as well as the list (I'm on the digest, which gets huge). TIA, Tom Roche <tom_ro...@pobox.com> ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
