MATLAB: Partial Fraction Expansion Issue/Question – confusing result

MATLABpartial fraction expansiontransfer function

Hi all,

I tried to find the partial fraction expansion of a transfer function, and was given a confusing result.

This screenshot is my result. I'm confused by the last line in the p matrix. How can I have a number in the numerator (last line of r), but have 0+0i in the denominator? Is there a mistake in my original denominator a and numerator b?

This screenshot above is my numerator, denominator, and residue function.

Best Answer

It just appears to be confusing.

The Symbolic Math Toolbox partfrac function gives:

or with the fractions rationalised:

So perhaps that will help to explain it.

Related Solutions

MATLAB: How to get improper fraction representation from rat(x,tol) function

[N,D] = rat(x,tol);

MATLAB: How to get the coefficients of the minimal polynomial

Hi Palash,

I think the following MATLAB function could do the job for your problem:

function p = minpoly(A)
p = evalin(symengine, ['map(poly2list(linalg::minpoly(' char(sym(A)) ',x)),c->c[1])']);
end

If you add it in MATLAB to your path, then you can call it via:

>> A = [1 -1 -1; 1 -2 1; 0 1 -3]; % minimal polynomial is x^3 + 4*x^2 + x - 1
>> minpoly(A)
ans =
[ 1, 4, 1, -1]

Hope this helps. Inside of MuPAD the function 'poly2list' converts polynomials to a nested list representation containing the information on the coefficients of polynomials.

Best regards,

-- Kai

Best Answer

Related Solutions

MATLAB: How to get improper fraction representation from rat(x,tol) function

MATLAB: How to get the coefficients of the minimal polynomial

Related Question