Model checking for gam (mgcv) result
The curve is caused by the zeroes in your data. raw.residual = response - fitted so if response=0 then raw.residual = -fitted. You get a curve, rather than a straight line, on the fitted vs residual plot because the residuals are standardised in a way that also depends on the fitted value. (This happens with other GLMs too, not just GAMs) best, Simon
On 12/04/11 16:02, Samuel Turgeon wrote:
Dear list, i'm checking the residuals plots of a gam model after a processus of model selection. I found the "best" model, all my terms are significant, the r-square and the deviance explained are good, but I have strange residuals plots: http://dl.dropbox.com/u/1169100/gam.check.png http://dl.dropbox.com/u/1169100/residuals_vs_fitted.png What does explains the "curve" on those plots?? I've also plotted each explanatory variables included in the model against residuals and everything looks fine. Kind regards, Sam [[alternative HTML version deleted]]
______________________________________________ R-help at 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.
Simon Wood, Mathematical Science, University of Bath BA2 7AY UK +44 (0)1225 386603 http://people.bath.ac.uk/sw283