[R] apply(ing) to sum subset of a vector
Jacques VESLOT
jacques.veslot at cirad.fr
Mon Mar 27 11:45:25 CEST 2006
apply(cbind(from,to), 1, function(x) sum(g[x[1]:x[2]]))
Fred J. a écrit :
>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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>
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