The loess.demo function in the TeachingDemos package helps visualize what is happening with the loess algorithm, it may answer some of your questions.
Simply, the span can be greater than 1, a span of 3/4 mean use the 3/4 of the points closest to where you are trying to predict, a span of 1 means use all the points (but their weights will change for where you are predicting), spans greater than 1 still use all the points, but the weights become more similar to each other, as span approaches Inf, the loess curve approaches a straight line. Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of rkevinbur...@charter.net > Sent: Thursday, November 19, 2009 4:03 PM > To: r-h...@stat.math.ethz.ch > Subject: [R] loess smoothing > > Hello, > > In reading the loess description I see: > > span: the parameter alpha which controls the degree of smoothing. > > The default seems to be 0.75. Would it be possible to expand on this > decription so I can avoid trail and error? Can I increase this pass > 'span' > 1? Qualitatively to what degree changing this value affects > the smoothing of the data? > > Thank you. > > Kevin > > ______________________________________________ > 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. ______________________________________________ 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.
