[R] Testing additive nonparametric model

[vito muggeo]

You can use the LRT (although I think that it assumes the df to be 
fixed). For instance the package mgcv by Simon Wood has an anova method 
to compare models fitted by the relevant gam() function, and the 
print.summary() itself returns such information..

best,
vito

set.seed(123)
n<-100
sig<-2
x0 <- runif(n, 0, 1)
x1 <- runif(n, 0, 1)
y <- sin(2*pi*x0) + .5*x1 +sig*rnorm(n)
library(mgcv)
obj<-gam(y~s(x0)+s(x1))
obj1<-gam(y~s(x0)+x1)
anova(obj1,obj,test="F")
#also see the "Approximate significance of smooth terms"
summary(obj)




Donal O'Neill wrote:
> I have estimated a multiple nonparametric regression using the loess 
> command in R. I have also estimated an additive version of the model using 
> the gam function. Is there a way of using the output of these two models to 
> test the restrictions imposed by the additive model?
> 
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-- 
====================================
Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
Università di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 6626240
fax: 091 485726/485612