You have the correct general idea, but it looks like lp may have already been transformed to be in the range 0-1 rather than number of days, if that is the case then you don't need to dived by 29. Again.
-- 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 Tim Clark > Sent: Thursday, April 29, 2010 5:50 PM > To: r-help@r-project.org > Subject: [R] Periodic regression - lunar percent cover > > Dear List, > > I am trying include a lunar variable in a model and am having problems > figuring out the correct way to include it. I want to convert the > percent lunar illumination (fraction of moon showing) to a combination > of sin and cos variables to account for the periodic nature of the > lunar cycle. Would someone let me know if I am doing this correctly? > I have included the first 20 variables from my dataset as an example. > Y is count data and lp is the lunar percent cover. The lunar period is > 29.53. > > y<-c(1, 3, 0, 0, 0, 0, 2, 4, 0, 1, 0, 5, 3, 2, 4, 2, 0, 1, 3, 5) > lp<-c(0.80, 0.88, 0.62, 0.19, 0.21, 0.01, 0.70, 1.00, 0.88, 0.04, 0.70, > 0.93, 0.23, 0.99, 0.19, 0.79, 1.00, 0.03, 0.01, 0.00) > g1<-glm(y~cos((2*pi*lp)/29.530589)+sin((2*pi*lp)/29.530589)) > > Thanks, > > Tim > > > > > Tim Clark > Department of Zoology > University of Hawaii > > ______________________________________________ > 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.
