[R-sig-ME] p-values in lme vs gamm

[Christoph Scherber]

Dear Etienne,

You should only compare the estimates and SE´s (and P values) from corresponding lme models:

summary(lme.mod)
summary(gamm.mod$lme)

These give exactly identical results.

Looking at the gam model without explicitly specifying a smoothing function s() does not make too much sense.

Best wishes
Christoph





Etienne Laliberté wrote:

> With gamm from the mgcv package, I'm struggling to understand the
> difference between summary(mymodel$gam) and summary(mymodel$lme).
> 
> In particular, can someone enlighten me as to why some of the p-values
> differ with the following two calls? Without smoothers, I thought gamm
> would simply give the same results as lme().
> 
> library(mgcv)
> data(oats)
> lme.mod <- lme(Y ~ N + V, random = list(B = ~1 , V = ~1), data = oats,
> method = "REML")
> gamm.mod <- gamm(Y ~ N + V, random = list(B = ~1 , V = ~1), data = oats,
> method = "REML")
> summary(lme.mod)
> summary(gamm.mod$gam)
> # note different p-values for VMarvellous and VVictory
> 
> Thanks
> 
> Etienne
> 
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