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

Spencer Graves spencer.graves at pdf.com
Mon Nov 1 22:35:25 CET 2004

```      Have you considered "cumsum(exp(-polynomial))"?

Consider for example the following:

library(polynom)
b. <- polynomial(1:5)

x <- seq(-2, 2, length=101)
b.p <- predict(b., x)

plot(x, b.p)
plot(x, exp(-b.p))

cdf <- cumsum(exp(-b.p))
plot(cdf/cdf[101])

hope this helps.  spencer graves

Yong Wang wrote:

> 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
>
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