MATLAB: How to numerical integrate polynomial coefficients to a high order

Question

Hello,

I have the coefficients of a polynomial of order 12 given to me using polyfit (it was fitted to model a probability density function). I now need to use the given polynomial f(x), multiply it by x^2, and integrate it over a given boundary.

I have tried using the integral function: integral(fun,xmin,xmax), where: fun = @(x) poly2sym(f) and f is the coefficients given by polyfit, but this doesn't work.

Any ideas? Apologies if this seems trivial, I have tried everything!

Thanks in advance, Rajin

Answer 1

Suppose p is a polynomial in MATLAB (a vector of coefficients). Multiplying by x^2 and integrating could be done by

Q = integral(@(x)polyval([p,0,0],x),xmin,xmax)

But how about

pint = polyint([p,0,0]);
Q = polyval(pint,xmax) - polyval(pint,xmin);