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

From: Gustaf Rydevik <gustaf.rydevik_at_gmail.com>
Date: Wed, 23 Jul 2008 17:35:48 +0200

On Wed, Jul 23, 2008 at 4:03 PM, Shubha Vishwanath Karanth <shubhak_at_ambaresearch.com> wrote:
> Hi R,
>
>
>
> Let,
>
>
>
> 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?
>
>
>
> Thanks, Shubha
>
>

How about

x<-1:80
filter(x,rep(1,8),"convolution",sides=1)[seq(8,length(x),by=8)] ##or
cumsum(x)[seq(8,length(x),by=8)]

?

/Gustaf

-- 
Gustaf Rydevik, M.Sci.
tel: +46(0)703 051 451
address:Essingetorget 40,112 66 Stockholm, SE
skype:gustaf_rydevik

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Received on Wed 23 Jul 2008 - 16:51:27 GMT

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