[R] n-dimensional vector operations
Ken-JP
kfmfe04 at gmail.com
Tue Apr 21 06:24:39 CEST 2009
Peter,
Thank you for your array() hint for multi-dimensional matrices.
Actually, my final answer should be of dimension 5,3,2 because my
funcp(a,b,c) will be reduced to one number when I set a to a column of x, b
to a column of y, and c to a column of z.
I did make some useful observations, though:
1. expand.grid() is useful for determining all the permutations of indexes I
need to use on the columns of x,y,z: for example: expand.grid( 1:5, 1:3,
1:2 ) or expand.grid( list( 1:5, 1:3, 1:2 )); # the last one is useful when
I don't know how many dimensions I need to go - eg I may have 7 matrices.
2. I hate to do it, but memory usage can blow up really fast, so it looks
like I need to do some nested looping to get the job done - maybe I can
change these to xapply() later.
- Ken
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