Possible bug with dredge function

Tue, Dec 13, 2011 11:01 AM

Hi, Fernando.

The warning message "In mer_finalize(ans) : gr cannot be computed at
initial par (65)" points to problems during the iterative process of
model fitting. This may be caused by the complexity of the global
model you're implying. Have you tried using dredge() with a simpler
global model (e.g. without interactions)?

2011/12/14, Fernando Schmidt <schmidt.fa at gmail.com>:

Dear colleagues,

I am working with information-theoretic based on the second-order AKaike?s
Information criterion corrected for small samples sizes AICc.  I have run
the mixed-effect models with ?glmer? function in the lme4 package. Then, I
used the dredge function from the MuMIn package to test models defined by
all possible variables combinations and rank them by AICc-based model
weight.

Usually, the main results from dredge function are AICc, delta and weight.
However, for one model seems to have some ?bug? I just could get AICc.
Delta and weight were missing:

mfullepi1<-glmer(sepi~lhet+ldth+transect+lhet:transect+(1|park/transect),family="poisson")

dredge(mfullepi1)

Global model: glmer(formula = sepi ~ lhet + ldth + transect + lhet:transect
+

    (1 | park/transect), family = "poisson")

---

Model selection table

   (Int)  ldt      lht     trn lht:trn k      Dev.            AICc

5  1.1630                  +                   14     97.79        129.8

7  1.0000           0.5228 +            15     95. 62       130.2

6  0.9803 0.002208         +          15    96.32        130.9

8  0.8236 0.002160  0.5188 +    16   94.17       131.5

3  1.4120           0.5538                    4   124.30      132.7

4  1.2810 0.002287  0.5153           5   122.40     132.9

2  1.3920 0.002544                          4   125.00     133.3

1  1.5480                                             3   127.20     133.4

15 1.4660          -1.0140 +   +       26

16 1.2560 0.002198 -0.9244 +   +       27

Random terms: 1 | park/transect

Mensagens de aviso perdidas:

1: In mer_finalize(ans) : gr cannot be computed at initial par (65)

2: In mer_finalize(ans) : gr cannot be computed at initial par (65)



Please, someone could explain me what is going on?



Thanks a lot!

All the best,

Fernando


--
Fernando Augusto Schmidt
Lab. de Ecologia de Comunidades
PPG - Entomologia. Universidade Federal de Vi?osa
Vi?osa, MG - Brazil 36570-000
www.labecol.ufv.br
+55 3182388810

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Pedro A. C. Lima Pequeno
Programa de P?s-gradua??o em Ecologia
Instituto Nacional de Pesquisas da Amaz?nia
Manaus, AM, Brasil

Possible bug with dredge function

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