try :
x2<-x[1:(length(x)-2)]-x[3:length(x)] OR x2<-diff(x,lag=2)
Hope it helps.
Gianluca wrote:
Hi all,
I'm back to use S-Plus after a lot programming with SAS, so it's hard for me to face many simple problems....
Let's come to what is going to make me crazy. I have a simple 1000 obs time series, called "x".
If I want to compute second order differences just typing:
x2<-x[1:length(x)-2]-x[3:length(x)]
but I get the following error message:
Error in x[1:length(x) - 2]: Only 0's may be mixed with negative subscripts
Much more interesting is that with first order differences it works perfectly....
Thanks in advance to all.
Gianluca
-- Kenneth Roy Cabrera Torres Celular +57 (315) 405 9339
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