ordinal (version 2019.4-25)

anova.clm2: Likelihood ratio test of cumulative link models

Description

Comparison of cumulative link models in likelihood ratio tests. The models may differ by terms in location, scale and nominal formulae, in link, threshold function and random effect structure.

Usage

# S3 method for clm2
anova(object, ..., test = c("Chisq", "none"))
# S3 method for clmm2
anova(object, ..., test = c("Chisq", "none"))

Arguments

object

a clm2 object.

…

one or more additional clm2 objects.

test

if test = "none" the p-value for the likelihood ratio test is suppressed.

Value

The method returns an object of class Anova (for printing) and data.frame with the following elements

Model

character description of the cumulative link models being compared. Location, scale and nominal formulae are separated by "|"s in this order.

Resid.df

the residual degrees of freedom

-2logLik

twice the negative log likelihood (proportional to the deviance)

Test

indication of which models are being compared.

DF

the difference in the degrees of freedom in the models being compared, i.e. the degrees of freedom for the chi-squared test.

LR stat.

the likelihood ratio statistic.

Pr(Chi)

the p-value from the likelihood ratio test. Absent if test = "none".

See Also

clm2, addterm, dropterm and anova.default

Examples

# NOT RUN {
options(contrasts = c("contr.treatment", "contr.poly"))
m1 <- clm2(SURENESS ~ PROD, scale = ~PROD, data = soup,
          link = "logistic")

## anova
anova(m1, update(m1, scale = ~.-PROD))
mN1 <- clm2(SURENESS ~ 1, nominal = ~PROD, data = soup,
           link = "logistic")
anova(m1, mN1)
anova(m1, update(m1, scale = ~.-PROD), mN1)

## Fit model from polr example:
if(require(MASS)) {
    fm1 <- clm2(Sat ~ Infl + Type + Cont, weights = Freq, data = housing)
    anova(fm1, update(fm1, scale =~ Cont))
}

# }