Many Thanks Jorge... That was one more way...Is it possible if I can do
this without using rep(1:10,each=8) or the grouping....because I feel
the number 8 here is fixed... If there is some technique of tracking the
position of first 8, then next 8... don't know whether I am clear in
conveying... 

 

Thanks, shubha

 

________________________________

From: Jorge Ivan Velez [mailto:jorgeivanvelez@gmail.com] 
Sent: Wednesday, July 23, 2008 8:59 PM
To: Shubha Vishwanath Karanth
Cc: r-help@stat.math.ethz.ch
Subject: Re: [R] sequential sum of a vector...




Dear Shubha,

Try this:

x=1:80
tapply(x,rep(1:10,each=8),sum)
 1   2   3   4   5   6   7   8   9  10 
 36 100 164 228 292 356 420 484 548 612 

HTH,

Jorge



On Wed, Jul 23, 2008 at 10:03 AM, Shubha Vishwanath Karanth
<shubhak@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



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