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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