betaPlot: beta density plot

Description

nice plot of beta density distribution

Usage

betaPlot(shape1=1.5, shape2=5, lines=NA, fill=rgb(0,0.3,0.8, 0.4),
cumulative=TRUE, mar=c(2,3,3,3), las=1,
main=paste("Beta density with\nalpha =", signif(shape1,2),
           "and beta =", signif(shape2,2)),
ylim=lim0(y), xlim=0:1, ylab="", xlab="",
type="l", lty=1, col=par("fg"), ... )

Arguments

shape1

alpha value as in dbeta. DEFAULT: 1.5

shape2

beta value. DEFAULT: 5

lines

at which quantiles should vertical lines be plotted? DEFAULT: NA

fill

color passed to polygon. DEFAULT: rgb(0,0.3,0.8, 0.4)

cumulative

should cumulative density distribution be added? DEFAULT: TRUE

mar

margins for plot passed to par. DEFAULT: c(2,3,3,3)

las

arguments passed to plot. DEFAULT: 1

main

main as in plot. DEFAULT: paste("Beta density with\nalpha =", shape1, "and beta =", shape2)

ylim, xlim

limit for the y and x axis. DEFAULT: lim0(y), 0:1

ylab, xlab

labels for the axes. DEFAULT: ""

type, lty, col

arguments passed to plot and lines.

...

further arguments passed to plot like lwd, xaxs, cex.axis, etc.

Value

None. Used for plotting.

Details

This function very quickly plots a beta distribution by just specifying alpha and beta.

Examples

Run this code

betaPlot()
betaPlot(2,1) 
betaPlot(0.5, 2)

# overview of parameters beta distribution:
# a bigger: HDI (Highest Density Interval) more to the left
# b bigger: HDI left, lower values
# both bigger: narrower HDI
a <- b <- c(0.5, 1:4)
par(mfrow=c(length(b), length(a)), yaxt="n", xaxt="n", 
    oma=c(2,2,4.5,2), mgp=c(3,0.7,0))
for(y in b)
  for(x in a)
  {
  betaPlot(x,y, main="", ylim=c(0.12,3), mar=rep(0,4), xaxs="r")
  mtext(text=paste("a=",x,", b=",y, sep=""), side=3, line=-1.5, cex=0.7)
  if(y==min(b)) mtext(paste("a =",x), side=3, line=0.5)
  if(x==min(a)) mtext(paste("b =",y), side=2, line=0.5)
  if(y==max(b) & x==median(a)) axis(1, at=c(0,0.5,1), xaxt="s", las=1)
  if(x==max(a) & y==median(b)) axis(4, at=0:3, yaxt="s", las=1)
  }
mtext("beta density distribution", line=2.5, outer=TRUE, cex=1.2, font=2)
box("outer")