[R] extracting coefficients from lmer

[Dimitris Rizopoulos]

you can use something like:

Vcov <- vcov(lmer.fit, useScale = FALSE)
betas <- fixef(lmer.fit)
se <- sqrt(diag(Vcov))
zval <- betas / se
pval <- 2 * pnorm(abs(zval), lower.tail = FALSE)
###############
cbind(betas, se, zval, pval)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Jonathan Williams" 
<jonathan.williams at pharmacology.oxford.ac.uk>
To: "Ethz. Ch" <r-help at stat.math.ethz.ch>
Sent: Tuesday, January 10, 2006 11:54 AM
Subject: [R] extracting coefficients from lmer


> Dear R-Helpers,
>
> I want to compare the results of outputs from glmmPQL and lmer 
> analyses.
> I could do this if I could extract the coefficients and standard 
> errors
> from the summaries of the lmer models. This is easy to do for the 
> glmmPQL
> summaries, using
>
>> glmm.fit <- try(glmmPQL(score ~ x*type, random = ~ 1 | subject, 
>> data = df,
> family = binomial), TRUE)
>> summary(glmmPQL.fit)$tTable
>
> Linear mixed-effects model fit by maximum likelihood
> Data: df
>       AIC      BIC    logLik
>  1800.477 1840.391 -890.2384
>
> Random effects:
> Formula: ~1 | subject
>        (Intercept)  Residual
> StdDev:   0.6355517 0.9650671
>
> Variance function:
> Structure: fixed weights
> Formula: ~invwt
> Fixed effects: score ~ x * type
>                 Value Std.Error  DF    t-value p-value
> (Intercept) -0.0812834 0.2933314 294 -0.2771043  0.7819
> x1           0.4143072 0.4180624  98  0.9910176  0.3241
> type2        0.8509166 0.4084443 294  2.0833112  0.0381
> type3        0.6691275 0.4024369 294  1.6626894  0.0974
> type4       -0.7830413 0.4123851 294 -1.8988109  0.0586
> x1:type2     1.0643239 0.6791126 294  1.5672274  0.1181
> x1:type3    -0.7533085 0.5674532 294 -1.3275253  0.1854
> x1:type4    -0.0549616 0.5777216 294 -0.0951351  0.9243
> etc.
>
> However, there seems to be no route to extract the corresponding 
> information
> from the lmer model:-
>
>> lmer.fit=try(lmer(score~x*type+(1|subject), data=df, 
>> family=binomial,
> method='AGQ'),TRUE)
>> summary(lmer.fit)
>
> Generalized linear mixed model fit using AGQ
> Formula: score ~ x * type + (1 | subject)
>   Data: df
> Family: binomial(logit link)
>      AIC      BIC    logLik deviance
> 510.2616 550.1762 -245.1308 490.2616
> Random effects:
>     Groups        Name    Variance    Std.Dev.
>    subject (Intercept)     0.46269     0.68021
> # of obs: 400, groups: subject, 100
>
> Estimated scale (compare to 1)  1.019134
>
> Fixed effects:
>             Estimate Std. Error  z value Pr(>|z|)
> (Intercept) -0.087284   0.300896 -0.29008  0.77175
> x1           0.446289   0.428844  1.04068  0.29803
> type2        0.913571   0.418978  2.18047  0.02922 *
> type3        0.719023   0.412816  1.74175  0.08155 .
> type4       -0.839842   0.423021 -1.98534  0.04711 *
> x1:type2     1.112673   0.696629  1.59722  0.11022
> x1:type3    -0.809599   0.582089 -1.39085  0.16427
> x1:type4    -0.062235   0.592623 -0.10502  0.91636
> etc.
>
>> summary(lmer.fit)$tTable
> NULL
>> names(summary(lmer.fit))
> NULL
>> names(lmer.fit)
> NULL
>> lmer.fit$coef
> NULL
>
> So, then I tried to find out if lmer returns different information.
>> help(lmer)
> This says "see lmer-class" ->
>> help(lmer-class)
> No documentation for 'lmer - class' in specified packages and 
> libraries:
> you could try 'help.search("lmer - class")'
>
> So, then I tried
>> help.search('lmer-class')
>
> This returns
> Help files with alias or concept or title matching 'lmer-class' 
> using fuzzy
> matching:
> lmer-class(Matrix)               Mixed model representations
>
> So, I loaded library Matrix and tried again
>> library(Matrix)
>> help(lmer-class)
> No documentation for 'lmer - class' in specified packages and 
> libraries:
> you could try 'help.search("lmer - class")'
>
> If someone could tell me how to extract the Estimates and Std. 
> Errors from
> the lmer summary, I'd be very grateful. I would also be very 
> grateful if
> someone
> could let me know why the Estimates and Std. Errors from the lmer 
> model are
> both
> larger than those from the glmmPQL model.
>
> I am running R 2.2.1 on a Windows XP machine.
>
> Thanks,
>
> Jonathan Williams
>
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