Calculate Likelihood Ratio, AIC, and BIC for lme Objects
DESCRIPTION:
A method for the generic function anova() for objects inheriting from class lme.
USAGE: 
anova.lme(object, ...)
REQUIRED ARGUMENTS:
object:
an object inheriting from class lme, usually returned by lme() or nlme().
OPTIONAL ARGUMENTS:
...:
other objects inheriting from class lme.
VALUE:
When only one argument is given, a data frame with the estimated values, the approximate standard errors, and the z-ratios of the fixed effects is returned. Otherwise a data frame with the degrees of freedom, the loglikelihood, the Akaike Information Criterion (AIC), and the Bayesian Information Criterion (BIC) of each object is returned. Whenever two consecutive objects have different number of degrees of freedom, a likelihood ratio statistic, with the associated p-value is included in the returned data frame.
NOTE:
Likelihood ratio comparisons are not meaningful for objects fit using restricted maximum likelihood and with different fixed effects.
SEE ALSO:
lme , lme.object , nlme , nlme.object .
EXAMPLES: 
# Ovary.fit and Ovary.fit1 inherit from class lme
Ovary.fit <- lme(fixed = follicles ~ sin(2*pi*Time) + cos(2*pi*Time),
                 random = ~sin(2*pi*Time) + cos(2*pi*Time),
                 cluster = ~ Mare,
                 data = Ovary, re.block = list(1, 2:3),
                 re.structure = c("i","d"), serial.structure = "ar1",
                 var.function = "power")


Ovary.fit.ano <- anova(Ovary.fit, Ovary.fit1)


# prints using print.anova.lme method
Ovary.fit.ano
Response: follicles
Ovary.fit
 fixed: (Intercept),sin(2 * pi * Time),cos(2 * pi * Time)
 random: (Intercept),sin(2 * pi * Time),cos(2 * pi * Time)
 block: list(1, 2:3)
 covariance structure: identity,diagonal
 serial correlation structure: ar1
 variance function: power
Ovary.fit1
 fixed: (Intercept),sin(2 * pi * Time),cos(2 * pi * Time)
 random: (Intercept),sin(2 * pi * Time),cos(2 * pi * Time)
 block: list(1, 2:3)
 covariance structure: identity,diagonal
 serial correlation structure: ar2
 variance function: power
           Model Df    AIC    BIC  Loglik    Test Lik.Ratio  P value
 Ovary.fit     1  9 1567.4 1601.0 -774.72
Ovary.fit1     2 10 1564.8 1602.1 -772.40 1 vs. 2    4.6531 0.030999