Re: [R] sequential sum of a vector...

From: <Richard.Cotton_at_hsl.gov.uk>
Date: Wed, 23 Jul 2008 16:37:40 +0100


> x=1:80
>
> I want to sum up first 8 elements of x, then again next 8 elements of x,
> then again another 8 elements..... So, my new vector should look like:
>
> c(36,100,164,228,292,356,420,484,548,612)
>
> I used:
>
> aggregate(x,list(rep(1:10,each=8)),sum)[-1]
>
> or
>
> rowsum(x,group=rep(1:10,each=8))
>
> But without grouping, can I achieve the required? Any other ways of
> doing this?

This works:
colSums(matrix(x, nrow=8))

I'm not sure if you benefit over using the methods you described though.

Regards,
Richie.

Mathematical Sciences Unit
HSL



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