On Thu, 27 Mar 2008, Nuno Prista wrote: > Can someone explain me this spec.pgram effect? > > > > Code: > > > > period.6<-c(0,0,0,0,0,10,0,0,0,0,0,10,0,0,0,0,0,10,0,0,0,0,0,10,0,0,0,0,0,10 > ,0,0,0,0,0,10,0,0,0,0,0,10,0,0,0,0,0,10,0,0,0,0,0,10,0,0,0,0,0,10) > > period.5<-c(0,0,0,0,0,10,0,0,0,0,10,0,0,0,0,0,0,10,0,0,0,0,10,0,0,0,0,0,0,10 > ,0,0,0,0,10,0,0,0,0,0,0,10,0,0,0,0,10,0,0,0,0,0,0,10,0,0,0,0,10,0) > > > > par(mfrow=c(2,1)) > > > > spec.pgram(period.6, log="no") > > spec.pgram(period.5, log="no") > > > > > > The first series has period 6 and shows its periodicity in 1/6 and > harmonics. In the second series I was expecting to see a signal occurring at > frequency 1/5 but it does not. Can anybody explain me why?
Because it does not have period 5 but 12 .... With such short series tapering has some effect. Try x <- rep(c(0,0,0,0,0,10,0,0,0,0,10,0), 100) spec.pgram(x, log="no") > > > > Thanks in advance, > > > > Nuno > > > > ______________________________________________ > > Centro de Oceanografia - IO-FCUL, Portugal > > Center for Quantitative Fisheries Ecology - ODU, USA > > email: [EMAIL PROTECTED] ; [EMAIL PROTECTED] > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@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. > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@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.