I am trying to apply methods used by Chaloupka & Limpus (1997) ( http://www.int-res.com/articles/meps/146/m146p001.pdf) to my own turtle growth data.
I am having trouble with two things... 1) After the GAM is fit, the residuals are skewed. >m1 <- gam(growth~s(mean.size, bs="cr")+s(year,bs="cr",k=7)+s(cohort,bs="cr")+s(age,bs="cr"), data=grow, family=quasi(link="identity")) >plot(m1, scale=0) #figure attached Should I try fitting a GAMM to model the tendencies in the residuals? How? 2) Using the GAM, I am able to fit a cubic-b spline but I do not know how to determine the equation for this spline nor how to integrate it/differentiate it (to obtain plots similar to 3c & f in Chaloupka & Limpus (1997)). What should I do next? >size <- seq(100,600,along.with=fitted(m1)) >grw <- fitted(m1) >bspline3 <- gam(grw~s(size, bs="cr", k=3)) >plot(grw~size,ylab="Growth (mm/yr)", xlab="Curved Carapace Length (mm)") #figure attached >lines(fitted(bspline3)~size, lwd=2) Thank you very much for any help! Claudia
______________________________________________ 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.
