Re: [R] what does this warnings mean? and what should I do?

From: Spencer Graves <spencer.graves_at_pdf.com>
Date: Sat 17 Dec 2005 - 11:13:35 EST

          You actually received two different warning messages. The first 8 warnings read, "optim or nlminb returned message false convergence (8)", and the other 3 say, "... returned message singular convergence". The function "lmer" uses a nonlinear optimizer (either "optim" or "nlminb") to minimize an objective function. The first message says that the nonlinear optimizer was still reducing the objective function when it reached an iteration limit. If this were the only problem, you might consider increasing the iteration limits, maxIter, msMaxIter, niterEM and PQLmaxIt. However, the "singular convergence" message says that the estimated variance-covariance matrix of the observations became singular.

          Looking now at your output, I notice that "Corr" between "(Intercept)" and "trust.cz1" for the "Random Effects" "commid" is 1.000. This says that the structure of your data are not adequate to allow you to distinguish between random effects for "(Intercept)" and "trust.cz1" for "commid", while simultaneously estimating all the fixed effects you have in the model.

          If I were you, I'd start be deleting all the terms from the model that don't have a "Signif. code" beside it in the table of "Fixed effects" and then refit the smaller model, preferably also using 'method="AGQ"'. If I still get the same message from trying to fit the reduced model, I would conclude that the data are not adequate to distinguish between "(Intercept)" and "trust.cz1" for "commid". I would then delete "trust.cz1" from the model and go from there.

	  hope this helps.
	  spencer graves

ronggui wrote:

> I use lmer to fit a mixed effect model.It give some warnings.what does this warnings mean? and what should I do?
>
>
>>(fm2.mlm <- lmer(qd ~ edu + jiankang + peixun +hunyin + cadcj + age + age2 + sex + dangyuan + Comp.1 + Comp.2+trust.cz1 + (trust.cz1|commid), data = individual,na.action = "na.exclude",family="quasibinomial"))
>
> Generalized linear mixed model fit using PQL
> Formula: qd ~ edu + jiankang + peixun + hunyin + cadcj + age + age2 + sex + dangyuan + Comp.1 + Comp.2 + trust.cz1 + (trust.cz1 | commid)
> Data: individual
> Family: quasibinomial(logit link)
> AIC BIC logLik deviance
> 736.7059 821.8267 -349.3529 698.7059
> Random effects:
> Groups Name Variance Std.Dev. Corr
> commid (Intercept) 1.56413 1.25065
> trust.cz1 0.17922 0.42334 1.000
> Residual 0.89728 0.94725
> # of obs: 652, groups: commid, 39
>
> Fixed effects:
> Estimate Std. Error DF t value Pr(>|t|)
> (Intercept) -1.6115e-01 6.7997e-01 637 -0.2370 0.81274
> edu -5.2585e-02 4.1048e-02 637 -1.2810 0.20064
> jiankang -9.8243e-01 4.4645e-01 637 -2.2005 0.02813 *
> peixun -4.6307e-01 2.6397e-01 637 -1.7542 0.07988 .
> hunyin -1.2255e-02 2.8151e-01 637 -0.0435 0.96529
> hunyin -2.7726e-01 1.3846e+00 637 -0.2002 0.84136
> hunyin -2.9759e-01 8.7180e-01 637 -0.3414 0.73295
> cadcj 2.2366e-01 7.6467e-01 637 0.2925 0.77000
> age 9.3626e-02 4.0390e-02 637 2.3180 0.02076 *
> age2 -1.3095e-03 5.5104e-04 637 -2.3763 0.01778 *
> sex 3.9188e-01 1.9759e-01 637 1.9833 0.04776 *
> dangyuan -5.2558e-01 5.9091e-01 637 -0.8894 0.37410
> Comp.1 5.2463e-02 1.0309e-01 637 0.5089 0.61100
> Comp.2 -1.5048e-01 1.1435e-01 637 -1.3160 0.18863
> trust.cz1 -8.0709e-01 4.4632e-01 637 -1.8083 0.07103 .
> ---
> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
> There were 11 warnings (use warnings() to see them)
>

>>warnings()

>
> Warning messages:
> 1: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 2: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 3: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 4: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 5: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 6: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 7: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 8: optim or nlminb returned message false convergence (8)
> in: LMEopt(x = mer, value = cv)
> 9: optim or nlminb returned message singular convergence (7)
> in: LMEopt(x = mer, value = cv)
> 10: optim or nlminb returned message singular convergence (7)
> in: LMEopt(x = mer, value = cv)
> 11: optim or nlminb returned message singular convergence (7)
> in: LMEopt(x = mer, value = cv)
>
>
>>version

>
> _
> platform i386-pc-mingw32
> arch i386
> os mingw32
> system i386, mingw32
> status
> major 2
> minor 2.0
> year 2005
> month 10
> day 06
> svn rev 35749
> language R
>
>
>
>
>
>
> 2005-12-14
>
> ------
> Deparment of Sociology
> Fudan University
>
> My new mail addres is ronggui.huang@gmail.com
> Blog:http://sociology.yculblog.com
>
>
>
> ------------------------------------------------------------------------
>
> ______________________________________________
> 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
-- 
Spencer Graves, PhD
Senior Development Engineer
PDF Solutions, Inc.
333 West San Carlos Street Suite 700
San Jose, CA 95110, USA

spencer.graves@pdf.com
www.pdf.com <http://www.pdf.com>
Tel:  408-938-4420
Fax: 408-280-7915

______________________________________________
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 Dec 17 11:21:42 2005

This archive was generated by hypermail 2.1.8 : Sun 18 Dec 2005 - 02:27:55 EST