MATLAB: Collect the term with certain order

Question

Dear Everyone,

I have an extremely complicated multi-variablespolynomial expression.

For example,

z = a1 * x^2 + b1 * y^2 + c1* x^2 * y^2 + a2 * x^4 …..

I want to collect the coefficients of x^2, which is a1.

Everytime I use collect(z,x^2), it just returns a1*x^2 + c1* x^2* y^2 + a2 * x^4.

Does anyone have experience in extracting the exact term using collect function in Matlab?

Thanks,

Zongquan

Answer 1

See if:

[C, T] = coeffs(z, [x y]);

does what you want. The coefficients are in ‘C’ and the corresponding terms in ‘T’.