crosscutplot {DOS2}

Scatterplot Associated with the Cross-Cut Test

Description

A scatterplot of y against x, with the points used by the cross-cut test in black, and the remaining points in grey. See Figure 19.2 in "Design of Observational Studies", second edition.

Usage

crosscutplot(x, y, ct = 0.25, xlab = "", ylab = "", main = "", ylim = NULL)

Arguments

x

Variable to be plotted on the horizontal axis.

y

Variable to be plotted on the vertical axis.

ct

The quantile that defines the crosscut. By default, the crosscut is at the outer .25 of the data, the lower 25 percent and the upper 75 percent.

xlab

Label for the x axis.

ylab

Label for the y axis.

main

Title of the plot.

ylim

Limits for the y axis. See example.

Value

A scatter plot.

Author(s)

Paul R. Rosenbaum

References

Rosenbaum, P. R. (2016) <doi:10.1111/biom.12373> "The crosscut statistic and its sensitivity to bias in observational studies with ordered doses of treatment". Biometrics, 72(1), 175-183.

Rosenbaum, P. R. (2017) <doi:10.1214/17-STS621> "The general structure of evidence factors in observational studies". Statistical Science 32, 514-530.

Examples

# Figure 1 in Rosenbaum (2017)
data(periodontal)
attach(periodontal)
m<-matrix(1:2,1,2)
layout(m,widths=c(1,2))
boxplot(pcteither[z==1]-pcteither[z==0],ylab="Smoker-Control Difference",
        main="(i)",xlab="Matched Pairs",ylim=c(-100,100))
abline(h=0,lty=2)
crosscutplot(cigsperday[z==1],pcteither[z==1]-pcteither[z==0],
    ct=.2,ylab="Smoker-Control Difference",
    xlab="Cigarettes per Day",main="(ii)",ylim=c(-100,100))
abline(h=0,lty=2)
detach(periodontal)
layout(1)