[R] yaxis of density plot as counts/bandwidth

[Ido M. Tamir]

Dear all,

I would like to change the scale of a density plot 
to something that represents counts/bandwidth.

What I am actually plotting is density of genomic
data along the chromosome, and I need a simple
representation of e.g. genes/50000 bases.

pos <- c(123423,124313,124790,,....)
den <- density(pos,bw=50000)
plot(den, yaxt="n", ylab="features/50kb")
etc...

Is the following correct?

library("MASS")
par(mfrow=c(2,2))
hist(geyser$duration)
den <- density(geyser$duration)
plot(den)
hist(geyser$duration,breaks=20)
plot(den,yaxt="n", ylab="")
fm <- den$bw * max(den$y) * den$n
at <- pretty(c(0,max(den$y)), n=5)
lab <- pretty(c(0,fm), n=5)
axis(2,at=at[1:6],lab=lab[1:6])


thank you very much
ido