How to extract numerator and denominator coeficients from polynomial function to array

I have numerator/denominator in form of 10s^6+9s^5+8s^4...+1

and when i try to plot this through command sys=tf(num,den) i get error that it needs to be cell arrays of vectors so i need command that will make array fom me from numerator, denominator like this.

I do not want to write it by hand, i need some command for script that will do that for me. Through symbolic variables i get TF, then i evaluate it for numerator and denominator, now i need to make array from that to use it with tf() command.

Thanks

Answer 1

[Karl]

You can extract a vector of the coefficients of a symbolic polynomial using sym2poly():

% Create example symbolic polynomial.
syms s
rng('default');
coeffs0 = randi([-10 10],1,5);
polynomial = poly2sym(coeffs0, s)

polynomial = 

% Extract polynomial coefficients.
coefficients = sym2poly(polynomial)

coefficients = 1x5

7 9 -8 9 3

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[ahmed]

thanks!!!!

Answer 2

[Steven Lord]

Do you have separate symbolic expressions for the numerator and denominator or do you have the fraction created by dividing numerator by denominator?

syms x
N = x^2+2*x+3

N = 

D = x^3+3*x^2+6*x+10

D = 

F = N./D

F = 

If you have N and D, just use sym2poly as @Karl showed. If you only have F, though, you can use the numden function to extract the numerator and denominator.

[num, den] = numden(F)

num = 

den =