Message-ID: <4186AC1D.4040004@pdf.com>
Date: 2004-11-01T21:35:25Z
From: Spencer Graves
Subject: How to plot PDF which is in the form of orthogonal polynomial
In-Reply-To: <Pine.LNX.4.61.0411011442050.5905@aitken.uchicago.edu>
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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--
Spencer Graves, PhD, Senior Development Engineer
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