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How to get the coefficients of a fractional polynomial from syms?

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Vinothkumar Sethurasu
Vinothkumar Sethurasu on 29 Jul 2021
Answered: Paul on 29 Jul 2021
I have a application which produces fractional polynomial as output as shown below,
syms x,
F=29.0*x*(5.7e-4*x + (5.58e-4*(0.0549*x - 0.0124*x*(0.00449*x - 1.0))*(4.92e-4*x - 1.0))/(0.00101*x - 1.0) - 1.0) - 0.141*x - (1.0*(0.0549*x - 0.0124*x*(0.00449*x - 1.0))*(4.92e-4*x - 1.0))/(0.00101*x - 1.0)
I need to know the co-efficients of the polynomial (F).
  2 Comments
Vinothkumar Sethurasu
Vinothkumar Sethurasu on 29 Jul 2021
If we are going for simplification as kept, F=0
The result will be a polynomila of 'x' with order 6.
I need to find the co-efficients of that polynomial.

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Accepted Answer

Paul
Paul on 29 Jul 2021
If I correctly understand this comment (and I'm not sure I do), it sounds like you just want the coefficients of the numerator of F:
syms x
F=29.0*x*(5.7e-4*x + (5.58e-4*(0.0549*x - 0.0124*x*(0.00449*x - 1.0))*(4.92e-4*x - 1.0))/(0.00101*x - 1.0) - 1.0) - 0.141*x - (1.0*(0.0549*x - 0.0124*x*(0.00449*x - 1.0))*(4.92e-4*x - 1.0))/(0.00101*x - 1.0);
[num,den] = numden(F);
num,den
num = 
den = 
[coefficients,terms] = coeffs(num,'all')
coefficients = 
terms = 
But maybe that's still not the result you're looking for because the coeffiecients are those of a fourth order polynomial, not sixth order.

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