[R] Partial sum of a vector

[David Winsemius]

Per the help page rollapply needs to be given a zoo or ts object, so  
you just coerce the matrix to zoo:

 > data_m <- matrix(1:20, ncol=2)
 > data_q <-matrix(,nrow=7,ncol=2)
# then you can vectorize the process
 > data_q[,] <-rollapply(as.zoo(data_m[,]),4,FUN=sum)
 > data_q
      [,1] [,2]
[1,]   10   50
[2,]   14   54
[3,]   18   58
[4,]   22   62
[5,]   26   66
[6,]   30   70
[7,]   34   74

-- 
David Winsemius

On Mar 1, 2009, at 10:16 PM, Mohammad Sabr wrote:

> Thanks Jorge,
>
> I tried to use the rollapply function as follows:
>
> rollapply(data_m ,4 , sum, by =1 , by.column = TRUE)
>
> but it is giving me the following error message:
>
> Error in UseMethod("rollapply") : no applicable method for "rollapply"
>
> Is there any file that I need to install or update. I reinstalled  
> the zoo package but I still getting the previous problem.
>
> Thank you for your assistance,
>
>
> --- On Sun, 3/1/09, Jorge Ivan Velez <jorgeivanvelez at gmail.com> wrote:
>
> From: Jorge Ivan Velez <jorgeivanvelez at gmail.com>
> Subject: Re: [R] Partial sum of a vector
> To: "Mohammad Sabr" <mohammad_sabr at yahoo.com>
> Cc: r-help at r-project.org
> Date: Sunday, March 1, 2009, 10:49 PM
>
>
> Dear Mohammad,
>
>
> Take a look at the rollmean function in the zoo package.
>
>
> HTH,
>
> Jorge
>
>
> On Sun, Mar 1, 2009 at 9:29 PM, Mohammad Sabr  
> <mohammad_sabr at yahoo.com> wrote:
>
> I am trying to run a loop where I can sum parts of a matrix. For  
> example, I want at each step in the loop to sum the the next 4- 
> values of a vector. I tried to do the following but the result were  
> wrong:
>
> for (i in 4:T) {
> data_q[i-3,]=sum(data_m[i-3,]:data_m[i,])
> }
>
> can anyone please direct me on what should I do to run this loop  
> properly
>
> Thanks in advance
>        [[alternative HTML version deleted]]
>
>
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>
>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.