[R] Overlying a Normal Dist in a Barplot
bret at tamu.edu
Fri Jul 8 21:22:14 CEST 2005
Hopefully someone can shed some light on these questions as I had
little luck searching the archives (although I probably missed something
in my search due to the search phrase). I estimated multinomial
probabilities for some count data (number successful offspring) ranging
from 0 to 8 (9 possible response categories). I constructed a barplot
(using barplot2) and I want to "overlay" a normal distribution on the
figure (using rnorm (1000, mean, sd)). My intent is to show that using
a mean(and associated sd) estimated from discrete count data may not be
a valid representation of the distribution of successful offspring.
Obviously the x and y axes (as structured in barplot2) will not be
equivalent for these 2 sets of information and this shows up in my
1) Is it possible to somehow reconcile the underlying x-axis to the
same scale as would be needed to overly the normal distribution (e.g.
where 2.5 would fall on the normal density, I could relate it to 2.5 on
the barplot)? Then, using axis (side=4) I assume I could insert a
y-axis for the normal distribution.
2) Is lines(density(x)) the appropriate way to insert a normal
distribution into this type of figure? Should I use 'curve'?
If someone could point me in the right direction, I would appreciate
x<-rnorm(1000, 2.84, 1.57)
barplot2(testdata, xlab="Fledgling Number",
ylab="Probability", ylim=c(0, 1), col="black",
system i386, mingw32
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