[R] truehist and density plots

[carol white]

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?

Cheers,

Carol