On Tue, Jun 23, 2009 at 9:44 PM, Ista Zahn<[email protected]> wrote: > I've seen quicker ways to do it, but I've been using ggplot2 for this. > See examples below. > > On Tue, Jun 23, 2009 at 7:57 PM, AbouEl-Makarim > Aboueissa<[email protected]> wrote: >> Dear All: >> >> I need some help with graphing the critical regions of hypothesis testing. >> >> Consider the Z-test, assume Z=3.2, and alpha=0.05 (that is Z_(a.pha/2)=1.96. >> >> Then how to graph the rejection region in the following three cases: >> >> Left-tailed test > > library(ggplot2) > z <- seq(-4,4, by = .01) > Density <- dnorm(z) > criteria <- factor(rep("retain", length(z)), levels=c("retain", "reject")) > criteria[which(z < qnorm(.05))] <- "reject" > qplot(z,Density, geom=c("path","area"), fill=criteria) + > scale_fill_manual(values=c("grey40", "red"))
Here's how I'd do it. I don't know if it's much of an improvement, but at least the final example shows you how to do the two-tailed case: library(ggplot2) df <- data.frame(z = seq(-4, 4, length = 100)) base <- qplot(z, dnorm(z), data = df, geom = "area") base + geom_area(data = subset(df, z < qnorm(0.05)), fill = "red") base + geom_area(data = subset(df, z > qnorm(0.95)), fill = "red") base + geom_area(aes(group = sign(z)), data = subset(df, abs(z) > qnorm(1 - 0.05 / 2)), fill = "red") -- http://had.co.nz/ _______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-sig-teaching
