If I understand you correctly, 5-10 points is not near enough to fit anything beyond a simple linear trend unless you know a priori what the form of the "trend" is. Period.
Admitting that the data are insufficient is better than performing misleading analyses. * Cheers, Bert * My personal view. Others may disagree and offer more useful ways forward. On Sun, Feb 19, 2012 at 2:25 PM, Roy Mendelssohn <roy.mendelss...@noaa.gov> wrote: > > On Feb 19, 2012, at 9:46 AM, John Kohr wrote: > >> >> Hello everyone, >> >> I was looking for a way to classify time-series based on the curve-fit. I >> try to campute several trends so i was thinking to link each trend with a >> function. increase with exponential for example, increase and decrease with >> a gaussian etc. The possiblities are endless though and it seems that is not >> always working well, especially if you work on small time-series (of 5-10 >> points only - one point in the end of the time-series can make the nls >> function to not be able to find the best fit among all these functions). Is >> there any package doing something similar? or another technique that could >> capture such trends? I can't find any code or publication on that, so I >> guess is something that is tested and is not working? >> >> Any help is appreciated. >> >> Best, >> John > > One option you have is to use StructTS which fits what is essentially a > non-parametric trend (it is actually a local smooth of the data). That > should give you an idea of the time trend if you then prefer a functional > form for the trend. There are other packages that do similar analysis, > StructTS is built into the basic stat package. > > HTH, > > -Roy M > > > ********************** > "The contents of this message do not reflect any position of the U.S. > Government or NOAA." > ********************** > Roy Mendelssohn > Supervisory Operations Research Analyst > NOAA/NMFS > Environmental Research Division > Southwest Fisheries Science Center > 1352 Lighthouse Avenue > Pacific Grove, CA 93950-2097 > > e-mail: roy.mendelss...@noaa.gov (Note new e-mail address) > voice: (831)-648-9029 > fax: (831)-648-8440 > www: http://www.pfeg.noaa.gov/ > > "Old age and treachery will overcome youth and skill." > "From those who have been given much, much will be expected" > "the arc of the moral universe is long, but it bends toward justice" -MLK Jr. > > ______________________________________________ > 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. -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ 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.
