Dear R users

I am trying to sum selective elements of a vector but my solution

is not cutting it.

Example:

> g <- 1:5;

> from <- 1:3;

> to <- 3:5;

from to

1 3

2 4

3 5

so I expect 3 sums from g

1+2+3 that is 1 to 3 of g

2+3+4 that is 2 to 4 of g

3+4+5 that is 3 to 5 of g

my solution will not work.

sum.em <- function(g, c1, c2) sum(g[c1:c2])

apply(g, 1, sum.em, ...) I don't think so because apply is not

aware of the from and to. and if I f <- list(g, from, to) that will not fit with the second arg of apply.

thank you

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