Re: [R] Nonnormal Residuals and GAMs

2013-11-08 Thread Robert Rigby
Hi Colin, The GAMLSS package allows modelling of the response variable distribution using either Exponential family or non-Exponential family distributions. It also allows modelling of the scale parameter (and hence the dispersion parameter for Exponential family distributions) using explanatory

Re: [R] Nonnormal Residuals and GAMs

2013-11-07 Thread Simon Wood
If you use GCV smoothness selection then, in the Gaussian case, the key assumptions are constant variance and independence. As with linear modelling, the normality assumption only comes in when you want to find confidence intervals or p-values. (The GM Thm does not require normality btw. but I do

Re: [R] Nonnormal Residuals and GAMs

2013-11-06 Thread COLLINL
>>> The default functional link for mgcv::gam is "log", so I doubt that >> your theoretical understanding applies to GAM's in general. When Simon >> Wood wrote his book on GAMs his first chapter was on linear models, his >> second chapter was on generalized lienar models at which point he had >> wr

Re: [R] Nonnormal Residuals and GAMs

2013-11-06 Thread David Winsemius
On Nov 6, 2013, at 5:44 PM, Collin Lynch wrote: >> The default functional link for mgcv::gam is "log", so I doubt that > your theoretical understanding applies to GAM's in general. When Simon > Wood wrote his book on GAMs his first chapter was on linear models, his > second chapter was on general

Re: [R] Nonnormal Residuals and GAMs

2013-11-06 Thread Collin Lynch
> The default functional link for mgcv::gam is "log", so I doubt that your theoretical understanding applies to GAM's in general. When Simon Wood wrote his book on GAMs his first chapter was on linear models, his second chapter was on generalized lienar models at which point he had written over

Re: [R] Nonnormal Residuals and GAMs

2013-11-06 Thread David Winsemius
On Nov 6, 2013, at 12:46 PM, Collin Lynch wrote: > Greetings, My question is more algorithmic than prectical. What I am > trying to determine is, are the GAM algorithms used in the mgcv package > affected by nonnormally-distributed residuals? > > As I understand the theory of linear models the

[R] Nonnormal Residuals and GAMs

2013-11-06 Thread Collin Lynch
Greetings, My question is more algorithmic than prectical. What I am trying to determine is, are the GAM algorithms used in the mgcv package affected by nonnormally-distributed residuals? As I understand the theory of linear models the Gauss-Markov theorem guarantees that least-squares regression