Hi all,

I'm trying to model animal association patterns using a logistic mixed
effects model with several random effects, and I keep getting the below
non-convergence warning. Can anyone provide insight on what I am doing wrong
or how I can get my model to converge? I assume this warning is
problematic...does anyone have more insight?

*Warning message:*
*In mer_finalize(ans) : false convergence (8)*

In case it is helpful, below is a description of my parameters, followed by
my model script, and model output. Thanks for any feedback you can provide!

*Response variables*:
SucG= number of times two animals (IDs) are observed together in a given
month
FailG= number of times one ID is observed without the other in a given month

*Fixed effects*:
Age = categorical variable describing the age combination of two IDs
(AA=adult-adult, AJ=adult-juvenile, JJ=juvenile-juvenile)
Gender= categorical variable describing the gender combination of two IDs
(MM=male-male, MF=male-female, FF=female-female)
Related= categorical variable describing the relationship of two IDs
(R=related, U=unrelated)
PrevMonthG= continuous variable for the association index for two IDs in the
previous month (standardized)
Rainean2MA= continuous variable for the mean rainfall 2 months prior (a
proxy for current fruit availability, standardized)
EstrusAd3= categorical variable for the number of females that are sexually
receptive in a given month
FamilyDiff= continuous variable for the difference in family size between
two IDs

*Random effects*:
Month
PID - Pair ID (i.e., the identifier for every combination of ID pairs)
Actor1 - ID 1 involved in the association
Actor2 - ID 2 involved in the association
PID:Month - an observation-level random effect to account for
over-dispersion

*Script:*
mg=cbind(SucG,FailG)~Age+Gender+Related+PrevMonthGs+RainMean2MAs+factor(EstrusAd3)+FamilyDiff+(1|Month)+(1|PID)+(1|Actor1)+(1|Actor2)+(1|factor(Month):factor(PID))
glmer(mg,data=standard,family=binomial(link='logit'),nAGQ=1)->SM12
SM12

*Output: *
Number of levels of a grouping factor for the random effects
is *equal* to n, the number of observations
Warning message:
In mer_finalize(ans) : false convergence (8)
> SM12
Generalized linear mixed model fit by the Laplace approximation
Formula: mg
   Data: standard
   AIC   BIC logLik deviance
 25450 25555 -12709    25418
Random effects:
 Groups                    Name        Variance Std.Dev.
 factor(Month):factor(PID) (Intercept) 3.857    1.964
 PID                       (Intercept) 0.000    0.000
 Actor2                    (Intercept) 0.757    0.870
 Actor1                    (Intercept) 0.550    0.742
 Month                     (Intercept) 0.333    0.577
Number of obs: 5225, groups: factor(Month):factor(PID), 5225; PID, 666;
Actor2, 36; Actor1, 36; Month, 8

Fixed effects:
                   Estimate Std. Error z value Pr(>|z|)
(Intercept)         -0.9884     0.5732   -1.72    0.085 .
AgeAJ                0.2598     0.2099    1.24    0.216
AgeJJ                0.4971     0.4117    1.21    0.227
GenderMF             0.2440     0.2066    1.18    0.238
GenderMM             0.5163     0.3936    1.31    0.190
Related             -1.5553     0.1935   -8.04  9.2e-16 ***
PrevMonthGs          1.0444     0.0395   26.42  < 2e-16 ***
RainMean2MAs         0.6263     0.2531    2.47    0.013 *
factor(EstrusAd3)1  -0.1683     0.5988   -0.28    0.779
factor(EstrusAd3)2   0.4705     0.5870    0.80    0.423
FamilyDiff          -0.0612     0.0317   -1.93    0.053 .
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Correlation of Fixed Effects:
            (Intr) AgeAJ  AgeJJ  GndrMF GndrMM Relatd PrvMnG RnM2MA f(EA3)1
f(EA3)2
AgeAJ
-0.258
AgeJJ       -0.254
0.949
GenderMF    -0.343 -0.033
-0.032
GenderMM    -0.337 -0.038 -0.034
0.959
Related     -0.286  0.059  0.036  0.004
-0.010
PrevMonthGs -0.047 -0.025 -0.032 -0.008 -0.018
0.277
RainMen2MAs  0.304 -0.001 -0.001  0.000 -0.001  0.012
0.045
fctr(EsA3)1 -0.657  0.002  0.002  0.001  0.001 -0.014 -0.051
-0.536
fctr(EsA3)2 -0.536  0.002  0.002  0.001  0.001 -0.014 -0.049 -0.106
0.542
FamilyDiff   0.043 -0.104 -0.021  0.005  0.011 -0.313  0.089  0.004 -0.004
-0.004


-- 
Julie Rushmore
DVM/PhD Candidate
College of Veterinary Medicine
Odum School of Ecology
University of Georgia
Athens, GA 30605
http://ecology.uga.edu/rushmore

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