qreference: Simulate QQ reference plots

In DAAG: Data Analysis and Graphics Data and Functions

Simulate QQ reference plots

Description

This function computes the QQ plot for given data and specified distribution, then repeating the comparison for data simulated from the specified distribution. The plots for simulated data give an indication of the range of variation that is to expected, and thus calibrate the eye.

Usage

qreference(test = NULL, m = 30, nrep = 6, pch=c(16,2), distribution = function(x) qnorm(x, 
    mean = ifelse(is.null(test), 0, mean(test)), sd = ifelse(is.null(test), 
    1, sd(test))), seed = NULL, nrows = NULL, cex.strip = 0.75, 
    xlab = NULL, ylab = NULL) 

Arguments

test	a vector containing a sample to be tested; if not supplied, all qq-plots are for data simulated from the reference distribution
m	the sample size for the reference samples; default is test sample size if test sample is supplied
nrep	the total number of samples, including reference samples and test sample if any
pch	plot character(s)
distribution	reference distribution; default is standard normal
seed	the random number generator seed
nrows	number of rows in the plot layout
cex.strip	character expansion factor for labels
xlab	label for x-axis
ylab	label for y-axis

Value

QQ plots of the sample (if test is non-null) and all reference samples

Author(s)

J.H. Maindonald

Examples

# qreference(rt(30,4))

# qreference(rt(30,4), distribution=function(x) qt(x, df=4))

# qreference(rexp(30), nrep = 4)

# toycars.lm <- lm(distance ~ angle + factor(car), data = toycars)
# qreference(residuals(toycars.lm), nrep = 9)

DAAG documentation built on May 29, 2024, 9:13 a.m.