R help - Jan 2006 - A function slightly different from diff()

Hi,

I wonder if the following function has already been implemented in (some) R
(package):

                summ <- function(x, lag=1) # x is a vector
                        {
                            n <- length(x)
                            x[(1+lag):n] + x[1:(n-lag)]
                        }

which (I think) the only difference from diff() is "+" instead of
"-", for
differences=1.

Thank you,
Dimitri Szerman

This isn't a single function but its a simple expression:

x <- ts(1:10)  # test data
x + lag(x)



On 1/25/06, dimitrijoe at ipea.gov.br <dimitrijoe at ipea.gov.br>
wrote:
> Hi,
>
> I wonder if the following function has already been implemented in (some) R
> (package):
>
>                summ <- function(x, lag=1) # x is a vector
>                        {
>                            n <- length(x)
>                            x[(1+lag):n] + x[1:(n-lag)]
>                        }
>
> which (I think) the only difference from diff() is "+" instead of
"-", for
> differences=1.
>
> Thank you,
> Dimitri Szerman
>
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