[R] plot the chi square distribution and the histogram in the same graph

[Rubén Roa-Ureta]

leo_wa wrote:
> In the previous post ,i ask how to plot the  normal curve and the histogram
> in the same graph.if i want to know how to plot the chi square distribution
> to campare the data set ,how can i do that?
>   
You should make up your mind, is your random variable X (-inf,+inf) or 
Sum(X^2) (which obviously cann't take negative values)?
They are quite different.
Rubén