On Tue, 1 Sep 2009, dolar wrote:
Would like some tips on how to avoid loops as I know they are slow in R
If I understand your criterion (and calling your data.frame 'dat'):
criterion <- as.matrix(dist(dat$a)) <= 5 & outer(dat$a,dat$a,">=")
criterion %*% as.matrix(dat[, c("b","c")])
b c
1 5 2
2 11 11
3 13 14
4 11 14
HTH,
Chuck
i've got a data frame :
a b c
1 5 2
4 6 9
5 2 3
8 3 2
What i'd like is to sum for each value of a, the sum of b and the sum of c
where a equal to or less than (with a distance of 5)
i.e. for row three
we have a=5
i'd like to sum up b and sum up c with the above rule
since 5, 4 and 1 are less than (within a distance of 5) or equal to 5, then
we should get the following result:
a b c
5 13 14
the overall result should be
a b c
1 5 2
4 11 11
5 13 14
8 11 14
how can i do this without a loop?
--
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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