# ------------------------------------------------
# Program: Univariate3.R  
#  Author: Steven M. Boker
#    Date: Tue Sep 25 10:48:33 EDT 2007
#
# Provides examples of the use of QQ plots for the 
# visualization of univariate distributions
#
# ------------------------------------------------

library(lattice)

# ------------------------------------------------
# Read the iris data. 

iris <- data.frame(read.table("iris.dat", header=T))
summary(iris)
dim(iris)


# ------------------------------------------------
# Quantile plot of sepal length using the "plot" command. 

pdf("Uni3Qplot1.pdf", height=5, width=5)
tLength <- length(iris$sepal.length)
plot(c(1:tLength)/tLength, sort(iris$sepal.length),
    xlab = "Fraction Value",
    ylab="Sepal Length (cm)")
dev.off()

# ------------------------------------------------
# Quantile plot of sepal length using Trellis graphics 

pdf("Uni3Qplot2.pdf", height=5, width=5)
print(qqmath(~ sepal.length, 
    distribution=qunif, data=iris,
    aspect=1,
    xlab = list(label="Fraction Value",cex=1.25),
    ylab=list(label="Sepal Length (cm)",cex=1.25),
    scales=list(cex=1.25),
    main=list(label="Quantiles of Sepal Length",cex=1.25)
    ))
dev.off()

# ------------------------------------------------
# Quantile plot of sepal length conditioned by variety

pdf("Uni3Qplot3.pdf", height=4,width=7.5)
print(qqmath(~ sepal.length | variety,
    distribution=qunif,
    data=iris,
    panel = function(x, ...) {
        panel.qqmathline(x, ...)
        panel.qqmath(x, ...)
    },
    layout=c(3,1), 
    aspect=1,
    xlab = list(label="Fraction Value",cex=1.25),
    ylab=list(label="Sepal Length (cm)",cex=1.25),
    scales=list(cex=1.25),
    main=list(label="Quantiles of Sepal Length",cex=1.25)
    ))
dev.off()


# ------------------------------------------------
# Quantile-Normal plot of sepal length against normal distribution 

pdf("UniQQnorm1.pdf", height=5, width=5)
qqnorm(iris$sepal.length, 
    xlab = "Quantiles from Normal Distribution", 
    ylab = "Quantiles from Sample")
dev.off()


# ------------------------------------------------
# Quantile-Quantile plot of sepal.length against normal distribution 

pdf("UniQQnorm2.pdf", height=5, width=5)
print(qqmath(~ sepal.length, 
    distribution=qnorm, data=iris,
    prepanel = prepanel.qqmathline, 
    panel = function(x, ...) {
        panel.qqmathline(x, ...)
        panel.qqmath(x, ...)
    },
    aspect=1,
    xlab = list(label="Normal Distribution",cex=1.25),
    ylab=list(label="Sepal Length (cm)",cex=1.25),
    scales=list(cex=1.25),
    main=list(label="Quantiles of Sepal Length",cex=1.25)
    ))
dev.off()

# ------------------------------------------------
# Quantile-Quantile plot of sepal.length against normal distribution
# by the conditioning variable variety. 

pdf("UniQQnorm3.pdf", height=5, width=5)
print(qqmath(~ sepal.length | variety, 
    distribution=qnorm, data=iris,
    prepanel = prepanel.qqmathline, 
    panel = function(x, ...) {
        panel.qqmathline(x, ...)
        panel.qqmath(x, ...)
    },
    aspect=1,layout=c(2,2),
    xlab = list(label="Normal Distribution",cex=1.25),
    ylab=list(label="Sepal Length (cm)",cex=1.25),
    scales=list(cex=1.25),
    main=list(label="Quantiles of Sepal Length",cex=1.25)
    ))
dev.off()

# ------------------------------------------------
# Quantile-Quantile plot of sepal.length of Setosa versus Versicolor 

pdf("UniQQIris1.pdf", height=5, width=5)
print(qq(variety ~ sepal.length, 
    data=iris,
    subset=variety=="Setosa" | variety=="Versicolor",
    aspect=1,
    xlab = list(label="Versacolor",cex=1.25),
    ylab=list(label="Setosa",cex=1.25),
    scales=list(cex=1.25),
    main=list(label="Quantiles of Setosa vs Versacolor",cex=1.25)))
dev.off()