# This script plots three QQ-normal plots, for a normal, gamma, and t # distribution. # Set up the graphics device. par(mfrow = c(1, 3)) par(xaxs = "i") par(yaxs = "i") # Set some graphical parameters. standard.axis <- seq(from = -3, to = 3, by = 1) y.axis <- seq(from = -3, to = 3, by = 1) axis.size <- 1.5 point.type <- 16 label.size <- 1.5 size <- 0.8 # Set some simulation parameters. N = 200 # Plot the QQ normal plot for an actual normal sample. qqnorm(rnorm(N), xlim = c(-3, 3), ylim = c(-3, 3), main = "", ylab = "", xaxt = "n", yaxt = "n", bty = "n", cex.lab = label.size, pch = point.type, cex = size) axis(1, at = standard.axis, labels = standard.axis, cex.axis = axis.size) axis(2, at = standard.axis, labels = standard.axis, cex.axis = axis.size) # Plot the QQ normal plot for a gamma sample. qqnorm(rgamma(N, 2.5, 1.25), xlim = c(-3, 3), ylim = c(0, 8), main = "", ylab = "", xaxt = "n", yaxt = "n", bty = "n", cex.lab = label.size, pch = point.type, cex = size) axis(1, at = standard.axis, labels = standard.axis, cex.axis = axis.size) gamma.y.axis <- seq(from = 0, to = 8, by = 1) axis(2, at = gamma.y.axis, labels = gamma.y.axis, cex.axis = axis.size) # Plot the QQ normal plot for a t sample. qqnorm(rt(N, 4), xlim = c(-3, 3), ylim = c(-6, 6), main = "", ylab = "", xaxt = "n", yaxt = "n", bty = "n", cex.lab = label.size, pch = point.type, cex = size) axis(1, at = standard.axis, labels = standard.axis, cex.axis = axis.size) t.y.axis <- seq(from = -6, to = 6, by = 2) axis(2, at = t.y.axis, labels = t.y.axis, cex.axis = axis.size) # This seems as though it is figure 3.10, but things may have changed # from the May 15th version. dev.print(device = postscript, "3.11.eps", horizontal = TRUE)