spatial correlation with nlme (Javier Moreira)

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Message: 1
Date: Tue, 1 Aug 2017 22:43:30 -0300
From: Javier Moreira <javiermoreira at gmail.com>
To: r-sig-mixed-models at r-project.org
Subject: [R-sig-ME] spatial correlation with nlme
Message-ID:
	<CAEyHP-0=TXAbK-fpFH=otmJ0Tzkk_yJ_86K6-8L5MbxtbLQovw at mail.gmail.com>
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hi,
im trying to generate different models to account for spatial correlation.
Im using nlme package, and mixed models, in order to compare two models,
one that doesnt include the spatial correlation and one that does.

Its a nested design, one that has 4 leves,
BLOQUE/ AMBIENTE/ TRATAMIENTO/ SUBMUESTREO
Its a harvest set data, with multiple point of data/ treatment, so the last
level account for another term in the error for "sub-muestreo".

My first problem its, when i try to add de correlation term to the model, i
cant, when the random effects are taken to the level /SUBMUESTREO, and i
have to leave it to the level of TRATAMIENTO.
When i do that, i have 2 differences between models, the term accounting
for sub-muestreo, and the spatial correlation.

#MODELO 2##
attach(base_modelo3)
str(base_modelo3)
data1=base_modelo3
str(data1)
data1=groupedData(REND.~1|BLOQUE/AMBIENTE/TRATAMIENTO/SUBMUESTREO,
data=data1, units=list(y="(ton/ha)"))
data1$TRATAMIENTO =factor(data1$TRATAMIENTO)
data1$BLOQUE =factor(data1$BLOQUE)
data1$AMBIENTE =factor(data1$AMBIENTE)

modelo2_MM<-lme(REND.~1+TRATAMIENTO*AMBIENTE,
                 random=~1|BLOQUE/AMBIENTE/TRATAMIENTO/SUBMUESTREO,
                 weights=varComb(varIdent(form=~1|TRATAMIENTO)),
                 data=data1,
                 control=lmeControl(niterEM=150,msMaxIter=200))
summary(modelo2_MM)
anova(modelo2_MM)

##MODELO 4##

modelo4_MM<-lme(REND.~1+TRATAMIENTO*AMBIENTE,
                 random=~1|BLOQUE/AMBIENTE/TRATAMIENTO,
                 weights=varComb(varIdent(form=~1|TRATAMIENTO)),
                 correlation=corExp(form=~X+Y,nugget=T),
                 data=data1,
                 control=lmeControl(niterEM=150,msMaxIter=200))
summary(modelo4_MM)
anova(modelo4_MM)