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2012 Feb 22
3
gamlss results for EXP and LNO seem to have reversed AIC scores
Hi, I'm a bit puzzled by the gamlss fitting of exponential and lognormal data. Gamlss seems to think that exponentially distributed data fits better with a lognormal distribution, and vice versa. For example, X <- rexp(1000) Gexp <- gamlss(X~1,family=EXP) # X~1 is X tilde 1 GAMLSS-RS iteration 1: Global Deviance = 2037.825 GAMLSS-RS iteration 2: Global Deviance = 2037.825 Glno
2013 Oct 27
1
R-help Digest, Vol 128, Issue 29
...r (e.g. standard deviastion) [and also heterogeity in skewness and kurtosis parameters].of the response variable distribution. For parametric models a generalized likelihood ratio test can be used to test whether the heterogeity is needed. Alternatively a generalized Akaike information criterion (GAIC) can be used to compare models. Robert Rigby On Date: Sat, 26 Oct 2013 23:57:51 -0400 (EDT Collin Lynch < collinl@cs.pitt.edu> wrote Subject: [R] Heteroscedasticity and mgcv. I have a two part question one about statistical theory and the other about implementations in R. Thank you f...
2013 Oct 27
2
Heteroscedasticity and mgcv.
I have a two part question one about statistical theory and the other about implementations in R. Thank you for all help in advance. (1) Am I correct in understanding that Heteroscedasticity is a problem for Generalized Additive Models as it is for standard linear models? I am asking particularly about the GAMs as implemented in the mgcv package. Based upon my online search it seems that some