truehist and density plots

Hi,
I wanted to plot the histogram of a vector and then, plot the density function of subsets of the vector on the histogram. So I use truehist in MASS package and lines(density) as follows:

length(b) = 1000
truehist(b)
lines(density(b[1:100]))

however the density plot of the first 100 points exceeds the max of y axis (see attached). how is it possible to make a graphics so that the density plot of the subsets doesn't go beyond the maximum of all points in the complete set?

  

Hi Carol,
You can use the rescale function in the plotrix package to do things 
like this. Have a look at the example on the help page:

# scale one vector into the range of another
 normal.counts<-rnorm(100)
 normal.tab<-tabulate(cut(normal.counts,breaks=seq(-3,3,by=1)))
 normal.density<-rescale(dnorm(seq(-3,3,length=100)),range(normal.tab))
 # now plot them
 plot(c(-2.5,-1.5,-0.5,0.5,1.5,2.5),normal.tab,xlab="X values",
  type="h",col="green")
 lines(seq(-3,3,length=100),normal.density,col="blue")


Jim