Nonlinear Ordinal Regression

Usage

nordr(y, dist="proportional", mu, linear=NULL, pmu, 
pblock, wt=NULL, print.level=0, ndigit=10, gradtol=0.00001,
steptol=0.00001, fscale=1, iterlim=100, typsiz=abs(p),
stepmax=10*sqrt(p%*%p))

Arguments

y A vector of ordinal responses, integers numbered from one to the maximum value.
dist The ordinal distribution: proportional odds, continuation ratio, or adjacent categories.
mu User-specified function of pmu, and possibly linear, giving the logistic regression equation. This may contain a linear part as the second argument to the function. It may also be a language expression beginning with ~, specifying a logistic regression function for the location parameter. If neither is supplied, the location is taken to be constant unless the linear argument is given.
linear Language expression beginning with ~, specifying the linear part of the logistic regression function.
pmu Vector of initial estimates for the regression parameters.
pblock Vector of initial estimates for the block parameters: two less than the number of different ordinal values.
wt Weight vector for use with contingency tables.
others Arguments controlling nlm.

Description

nordr fits arbitrary nonlinear regression functions (with logistic link) to ordinal response data by proportional odds, continuation ratio, or adjacent categories.

Value

A list of class gnlr is returned. The printed output includes the -log likelihood (not the deviance), the corresponding AIC, the maximum likelihood estimates, standard errors, and correlations. A list is returned that contains all of the relevant information calculated, including error codes.

Examples

# McCullagh (1980) JRSS B42, 109-142
# Tonsil size: 2x3 contingency table
y <- c(1:3,1:3)
carrier <- gl(2,3,6)
wt <- c(19,29,24,497,560,269)
pmu <- c(-1,0.5)
mu <- function(p) c(rep(p[1],3),rep(p[1]+p[2],3))
# proportional odds with mean function
nordr(y, dist="prop", mu=mu, pmu=pmu, wt=wt, pbl=1.5)
# proportional odds using Wilkinson and Rogers notation
nordr(y, dist="prop", mu=~carrier, pmu=pmu, wt=wt, pbl=1.5)
# continuation ratio
nordr(y, dist="cont", mu=mu, pmu=pmu, wt=wt, pbl=1.5)
# adjacent categories
nordr(y, dist="adj", mu=~carrier, pmu=pmu, wt=wt, pbl=1.5)


[Package Contents]