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

[hidden email]
> Blog:

http://sociology.yculblog.com>

>

>

> ------------------------------------------------------------------------

>

> ______________________________________________

>

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>

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

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Tel: 408-938-4420

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