superimpose density line over hist

Le 13.12.2005 14:23, Albert Vilella a ??crit :

Hi all,

I'm trying to superimpose a rchisq density line over a histogram with
something like:

hist(alnlength)
lines(density(rchisq(length(alnlength), 4)),col="red")

But the rchisq line won't appear anywhere,

Anyone knows what I am missing here?

Thanks in advance,

   Albert.
 

Hi Albert,

A few comments :
- your code should be reproductible, otherwise it is useless. (that 
recommandation is on the posting guide)

- that question is a top ten question on that list, go to the archive 
and you will find answers. (also posting guide)
BTW, it should be a FAQ and what about an example of overlaying in hist 
help page ?

- then if you want to superimpose an histogram and a density curve, they 
should be on the same scale, it is not the case since you missed the 
argument freq in your hist call, it should be :

R> hist(alnlength, freq=FALSE)

- Why do you simulate points to draw the density line ? Give a shot at :

R> curve(dchisq, df=4, col="red")


- That might interrest you :
http://addictedtor.free.fr/graphiques/search.php?q=hist

Romain

visit the R Graph Gallery : http://addictedtor.free.fr/graphiques
mixmod 1.7 is released : http://www-math.univ-fcomte.fr/mixmod/index.php
+---------------------------------------------------------------+
| Romain FRANCOIS - http://francoisromain.free.fr               |
| Doctorant INRIA Futurs / EDF                                  |
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