[R-sig-ME] how to extract the degrees of freedom in lmer

[Anne Dubois]

Dear all,

Previously I was using "lme" and I could extract the denominator degrees 
of freedom   with : summary(fit)$tTable[,3]

Now, I am trying to do the same in "lmer" but I do not know if it is 
possible because the degrees of freedom does not appear in the summary. 
Can you help me, please ?

Thank you for your time.
Sincerely,

Anne Dubois (anne.dubois at inserm.fr)

PS : To illustrate my problem, I use the dataset ergoStool (see below)


 > Stool.lme<-lme(effort~Type,random=~1|Subject,data=ergoStool)
 > summary(Stool.lme)
Linear mixed-effects model fit by REML
 Data: ergoStool
       AIC      BIC   logLik
  133.1308 141.9252 -60.5654

Random effects:
 Formula: ~1 | Subject
        (Intercept) Residual
StdDev:    1.332465 1.100295

Fixed effects: effort ~ Type
               Value Std.Error DF   t-value p-value
(Intercept) 8.555556 0.5760123 24 14.853079  0.0000
TypeT2      3.888889 0.5186838 24  7.497610  0.0000
TypeT3      2.222222 0.5186838 24  4.284348  0.0003
TypeT4      0.666667 0.5186838 24  1.285304  0.2110
 Correlation:
       (Intr) TypeT2 TypeT3
TypeT2 -0.45              
TypeT3 -0.45   0.50       
TypeT4 -0.45   0.50   0.50

Standardized Within-Group Residuals:
        Min          Q1         Med          Q3         Max
-1.80200345 -0.64316591  0.05783115  0.70099706  1.63142054

Number of Observations: 36
Number of Groups: 9
 > summary(Stool.lme)$tTable[,3]
(Intercept)      TypeT2      TypeT3      TypeT4
         24          24          24          24



 > Stool.lmer<-lmer(effort~Type+(1|Subject),data=ergoStool)
 > summary(Stool.lmer)
Linear mixed model fit by REML
Formula: effort ~ Type + (1 | Subject)
   Data: ergoStool
   AIC   BIC logLik deviance REMLdev
 133.1 142.6 -60.57    122.1   121.1
Random effects:
 Groups   Name        Variance Std.Dev.
 Subject  (Intercept) 1.7753   1.3324 
 Residual             1.2107   1.1003 
Number of obs: 36, groups: Subject, 9

Fixed effects:
            Estimate Std. Error t value
(Intercept)   8.5556     0.5760  14.853
TypeT2        3.8889     0.5187   7.498
TypeT3        2.2222     0.5187   4.284
TypeT4        0.6667     0.5187   1.285

Correlation of Fixed Effects:
       (Intr) TypeT2 TypeT3
TypeT2 -0.450             
TypeT3 -0.450  0.500      
TypeT4 -0.450  0.500  0.500



-- 
Anne DUBOIS
INSERM UMR 738
16, rue Henri Huchard
75018 PARIS
Tel : 01 57 27 73 52
anne.dubois at inserm.fr