help with glmmPQL

HI, DOUG & JOSE:

      Is there some reason that "anova.lme" should NOT accept an
object of class "glmmPQL" in the example below?  If you don't see one
either, then I suggest you consider modifying the code as described
below.

HI, ANDREW:

      I couldn't find your data "learning" in my Windows installation
of R 2.0.0pat, which meant that I had to take the time to find
another example before I could get the error message you described. 
I got it from modifying the example in the documentation for
"glmmPQL" as follows:

fit1 <- glmmPQL(y ~ trt, random = ~ 1 | ID,
                     family = binomial, data = bacteria)
fit2 <- glmmPQL(y ~ trt + I(week > 2), random = ~ 1 | ID,
                     family = binomial, data = bacteria)
anova(fit1, fit2)
    Error in anova.lme(fit1, fit2) : Objects must inherit from
classes "gls", "gnls" "lm","lmList", "lme","nlme","nlsList", or "nls"

      I then checked the class of fit1 and fit2:

 > class(fit1)

[1] "glmmPQL" "lme"

 > class(fit2)

[1] "glmmPQL" "lme"

      As an experiment, I changed the class of fit1 and fit2:

 > class(fit1) <- "lme"
 > class(fit2) <- "lme"
 > anova(fit1, fit2)

     Model df      AIC      BIC    logLik   Test  L.Ratio p-value
fit1     1  5 1054.623 1071.592 -522.3117
fit2     2  6 1113.622 1133.984 -550.8111 1 vs 2 56.99884  <.0001

      Unless someone like Doug or Jose tells us, "Don't do that", I
would use these answers.

library(lme4)
data(bacteria, package = "MASS")
fit1 <- GLMM(y ~ trt, random = ~ 1 | ID, 

fit2 <- GLMM(y ~ trt + I(week > 2), random = ~ 1 | ID, 

logLik(fit1)

logLik(fit2)