[R-sig-eco] Function "density" _barplot

[momadou sow]

Hi,
I wanted crossed lines  in barplots afer the use of this code.
>test<-c(4,8,9,6,7)
>barplot(test,density =20,angle=45)
Please, how to do it? 
I attached an example showing  what I want to do. 
Thank you in advance.      
Momadou