## ----echo=FALSE,eval=FALSE----------------------------------------------------
# options(width=80)

## ----results='hide',eval=FALSE------------------------------------------------
# rm(list=ls(all=TRUE))
# library(catdata)
# data(knee)
# attach(knee)

## ----eval=FALSE---------------------------------------------------------------
# suppressWarnings(chisq.test(knee$Th,knee$R4))

## ----eval=FALSE---------------------------------------------------------------
# Age <- Age - 30
# Age2 <- Age^2

## ----eval=FALSE---------------------------------------------------------------
# R4 <- as.ordered(R4)
# Th <- as.factor(Th)
# Sex <- as.factor(Sex)

## ----eval=FALSE---------------------------------------------------------------
# library(MASS)

## ----results='hide',eval=FALSE------------------------------------------------
# polr1 <- polr(R4 ~ Th, method="logistic")

## ----eval=FALSE---------------------------------------------------------------
# summary(polr1)

## ----eval=FALSE---------------------------------------------------------------
# exp(-coef(polr1))

## ----results='hide',eval=FALSE------------------------------------------------
# polr2 <- polr(R4 ~ Th + Sex + Age, method="logistic")

## ----eval=FALSE---------------------------------------------------------------
# summary(polr2)

## ----eval=FALSE---------------------------------------------------------------
# exp(-coef(polr2))

## ----eval=FALSE---------------------------------------------------------------
# se <- summary(polr2)[1][[1]][1:3,2]
# (wald2 <- -coef(polr2)/se)

## ----eval=FALSE---------------------------------------------------------------
# 1-pchisq(wald2^2, df=1)

## ----results='hide',eval=FALSE------------------------------------------------
# polr3 <- update(polr2, ~. + Age2)

## ----eval=FALSE---------------------------------------------------------------
# summary(polr3)

## ----eval=FALSE---------------------------------------------------------------
# exp(-coef(polr3))

## ----eval=FALSE---------------------------------------------------------------
# se <- summary(polr3)[1][[1]][1:4,2]
# (wald3 <- -coef(polr3)/se)

## ----eval=FALSE---------------------------------------------------------------
# 1-pchisq(wald3^2, df=1)

## ----eval=FALSE---------------------------------------------------------------
# library(VGAM)

## ----eval=FALSE---------------------------------------------------------------
# m.vglm <- vglm(R4 ~ Th + Sex + Age + Age2, family = cumulative (link="logitlink",
# parallel=TRUE))
# summary(m.vglm)

## ----eval=FALSE---------------------------------------------------------------
# library(rms)

## ----eval=FALSE---------------------------------------------------------------
# m.lrm <- lrm(R4 ~ Th + Sex + Age + Age2)
# m.lrm

## ----echo=FALSE,eval=FALSE----------------------------------------------------
# detach(package:VGAM)