symbolic integration for chi-square distribution

I want to do following integration:

syms x y 
F = @(x,y)chi2pdf(y,2).*chi2pdf(x,1);
fp = int(int(F,y,x-3,100),x,0,100);

However, it does not show an explicit number. Is there any way to carry out the integration? Thank you.

Answer 1

[Walter Roberson]

Possibly you will have to go back to the definition of chi2pdf that is on the documentation page, http://www.mathworks.com/help/toolbox/stats/chi2pdf.html as chi2pdf routine is a numeric routine rather than a symbolic routine.

[Ikjin]

if chi-square distribution is used, then I can replace it with analytic expression. But, if non-central chi-square distribution is used, do you know how to do the integration?

[Walter Roberson]

There seems to be a formula at

http://en.wikipedia.org/wiki/Noncentral_chi-squared_distribution#Cumulative_distribution_function