[R] How to plot PDF which is in the form of orthogonal polynomial

[Yong Wang]

Dear all
using the orthogonal polymial on a set of data, I get an approximate 
density
which basically is in the form: exp(-polynomial),
  as you know, the parameters are the converged coeeficients.
obviously, It is hard, if not impossible, to use the inverse CDF method to 
get
a sample and then plot density. then how can I plot the approximated 
density in
order to have a graphical comparision with the real data's histogram.

any hint is appreciated

thanks