[R-sig-ME] lme4 glmer convergence question

[Sally A. Roman]

Hello -
I am trying to use the lme4 package for a glmm and am getting a convergence code of 0 and a statement: Model failed to converge with max|grad| = 0.00791467 (tol = 0.001, component 1). I am interested in using the lme4 package because I would like to have AIC values to determine the appropriate model as I add in additional covariates.

Two weeks ago when I tried the same approach I got a warning message that the model failed to converge because of the max|grad| issue, but am not getting the warning message this time, just the statement at the end of the summary output.

Summary output below:
Generalized linear mixed model fit by maximum likelihood (Laplace
  Approximation) [glmerMod]
Family: Gamma  ( log )
Formula: Meat_Weight ~ logsh + SAMS_region_2015 + (1 | StationID)
   Data: datad
Control: glmerControl(optCtrl = list(maxfun = 100000))

    AIC      BIC   logLik deviance df.resid
 29841.2  29893.0 -14912.6  29825.2     4748

Scaled residuals:
    Min      1Q  Median      3Q     Max
-5.6389 -0.5089  0.0376  0.5660  7.3199

Random effects:
Groups    Name        Variance Std.Dev.
StationID (Intercept) 0.007073 0.0841
 Residual              0.026626 0.1632
Number of obs: 4756, groups:  StationID, 426

Fixed effects:
                     Estimate Std. Error t value             Pr(>|z|)
(Intercept)          -9.21833    0.10890  -84.65 < 0.0000000000000002
logsh                 2.62984    0.02223  118.33 < 0.0000000000000002
SAMS_region_2015ET    0.09299    0.03174    2.93             0.003393
SAMS_region_2015HC    0.12031    0.03347    3.59             0.000325
SAMS_region_2015HCsr  0.08405    0.03892    2.16             0.030810
SAMS_region_2015LI    0.07721    0.03209    2.41             0.016107

(Intercept)          ***
logsh                ***
SAMS_region_2015ET   **
SAMS_region_2015HC   ***
SAMS_region_2015HCsr *
SAMS_region_2015LI   *
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Correlation of Fixed Effects:
                 (Intr) logsh  SAMS__2015E SAMS_regn_2015HC
logsh            -0.968
SAMS__2015E      -0.179 -0.036
SAMS_regn_2015HC -0.166 -0.038  0.699
SAMS_rgn_2015HCs -0.139 -0.037  0.600       0.569
SAMS__2015L      -0.186 -0.027  0.728       0.691
                 SAMS_rgn_2015HCs
logsh
SAMS__2015E
SAMS_regn_2015HC
SAMS_rgn_2015HCs
SAMS__2015L       0.593
convergence code: 0
Model failed to converge with max|grad| = 0.00764043 (tol = 0.001, component 1)

Does this mean that the model is not converging? I also used the glmmPQL method. The coefficient parameter estimates are similar between the two model types.

Here is glmer (lme4) model code. I increased the maxfun to deal with other issues I had when I ran the model last time.

l1<-glmer(Meat_Weight~logsh+SAMS_region_2015+(1|StationID),
        family="Gamma"(link="log"),data=datad,control=glmerControl(optCtrl=list(maxfun=100000)))
Here is the glmmPQL code.

m1<-glmmPQL(fixed=Meat_Weight~logsh+SAMS_region_2015,random=~1|StationID,
        family=Gamma(link="log"),data=datad)

I am sure this is not information to diagnosis the problem, but if anyone has suggestions I can provide more data.

Thanks

Sally Roman
Fisheries Specialist
Virginia Institute of Marine Science
Marine Advisory Services

Phone: 804-684-7165
Fax: 804-684-7161

1375 Greate Road
Gloucester Point, VA 23062


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