VGAM (version 0.7-3)

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.

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)