Dear Rui and Murphy,
Thanks for your help.
Eliza

> Date: Fri, 9 May 2014 22:55:27 +0100
> From: ruipbarradas@sapo.pt
> To: eliza_botto@hotmail.com; r-help@r-project.org
> Subject: Re: [R] adding rows
> 
> Hello,
> 
> Try the following.
> 
> sapply(1:(30 - 2), function(i) sum(el[i:(i+2), ]))
> 
> 
> but with number of rows instead of 30.
> 
> Hope this helps,
> 
> Rui Barradas
> 
> Em 09-05-2014 22:35, eliza botto escreveu:
> > Dear useRs,
> > I have a matrix, say "el" of 30 rows and 10 columns, as
> > el<-matrix(sample(1:300),ncol=10)
> > I want to sum up various sets of three rows of each column in the following manner
> > sum(el[c(1,2,3),]) ##adding row number 1, 2 and 3 of each column
> > sum(el[c(2,3,4),])##adding row number 2, 3 and 4 of each column
> > sum(el[c(3,4,5),])##adding row number 3, 4 and 5 of each column
> > sum(el[c(4,5,6),])
> > sum(el[c(5,6,7),])
> > sum(el[c(6,7,8),])
> > sum(el[c(7,8,9),])
> > sum(el[c(8,9,10),])
> > sum(el[c(9,10,11),])
> > ................
> > ......
> > so on
> > ..............
> > I know how to do it manually, but since my original matrix has 2000 rows, I therefore want to figure out a more conveinient way.
> > Thankyou so very much in advance,
> >
> > Eliza 		 	   		
> > 	[[alternative HTML version deleted]]
> >
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> >
 		 	   		  
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