From: Patricia Balvanera <pbalvane_at_oikos.unam.mx>

Date: Sat 16 Jul 2005 - 02:12:26 EST

* > model5<-update(model2,corr=corSpher(c(30,0.8), form = ~ X + Y, nugget = T))
*

> plot(Variogram(modelo7, resType = "n"))

> summary(model5)

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat Jul 16 02:18:00 2005

Date: Sat 16 Jul 2005 - 02:12:26 EST

model1 3 3730.537 model2 4 3698.849 model3 6 3702.408 model4 4 3704.722

> plot(Variogram(model2, form = ~ X + Y))

> plot(Variogram(modelo7, resType = "n"))

> summary(model5)

In this case I obtain new F for the independent variable INSOLACION, new R2 for the whole model and new parameters for the linear model.

I have also applied this procedure to polinomial models and to glms with
binomial errors

(presence/absence) with no problem.

I am nevertheless stuck with non-linear models. I am using the protocols
you suggested

in the 1998 manuals by Pinheiro and Bates, and those suggested by Crawley
2002.

Please find enclose an example with an

exponential model (which I chose for being simple). In fact the linear
models I am using

are a bit more complicated.

(HELLOT is a species, INSOLACION = INSOLATION, basal = basal area of the
species, TRANSECTO = transect)

* > HELLOT ~ exp(A + (B * INSOLACION))
** > basal.HELLOT <-function(A,B,INSOLACION) exp(A + (B * INSOLACION))
*

> HELLOT ~ basal.HELLOT(A,B,INSOLACION)

> basal.HELLOT<- deriv(~ exp(A + (B * INSOLACION))

+ , LETTERS [1:2], function(A, B, INSOLACION){})

> model1<- nlme(model = HELLOT ~ exp(A + (B * INSOLACION)), fixed = A + B

~ 1,

random = A + B ~ 1, groups = ~ TRANSECTO, start = list(fixed = c(5.23, -0.05)))

It runs perfectly and gives new values for parameters A and B, but would only give me F for fixed effects of A and B, while what I am really looking for is F for fixed effects of INSOLACION and the R2 of the new model.

Thank you so much in advance for your help

Dra. Patricia Balvanera

Centro de Investigaciones en Ecosistemas, UNAM-Campus Morelia
Apdo. Postal 27-3, Xangari

58090 Morelia, Michoacán, Mexico

Tel. (52-443)3-22-27-07, (52-55) 56-23-27-07
**FAX (52-443) 3-22-27-19, (52-55) 56-23-27-19
**

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat Jul 16 02:18:00 2005

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