VGAM (version 0.7-6)

acat: Ordinal Regression with Adjacent Categories Probabilities

Description

Fits an adjacent categories regression model to an ordered (preferably) factor response.

Usage

acat(link = "loge", earg = list(),
     parallel = FALSE, reverse = FALSE, zero = NULL)

Value

• An object of class "vglmff" (see vglmff-class). The object is used by modelling functions such as vglm, rrvglm and vgam.

Warning

No check is made to verify that the response is ordinal; see ordered.

Details

By default, the log link is used because the ratio of two probabilities is positive.

References

Agresti, A. (2002) Categorical Data Analysis, 2nd ed. New York: Wiley.

Simonoff, J. S. (2003) Analyzing Categorical Data, New York: Springer-Verlag.

Documentation accompanying the VGAM package at http://www.stat.auckland.ac.nz/~yee contains further information and examples.

See Also

cumulative, cratio, sratio, multinomial, pneumo.

Examples

data(pneumo)
pneumo = transform(pneumo, let=log(exposure.time))
(fit = vglm(cbind(normal,mild,severe) ~ let, acat, pneumo))
coef(fit, matrix=TRUE)
constraints(fit)
model.matrix(fit)