Collect function doesn't work as intended

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Cesar Adolfo Cruz Vargaya
评论： Torsten 2022-11-1
Ran in:
syms z w K
% Previous steps executed, expresion directly copied from workspace
GzSFDen = 1.0*z^2 + (0.36788*K - 1.3679)*z + 0.26424*K + 0.36788;
GzSFDen = vpa(GzSFDen)
GzSFDen = 
% Substitution of z with (w+1)/(w-1)
Gw = subs(GzSFDen,z,(w+1)/(w-1))
Gw = 
% Obtained answer, coefficient of w^2 should only be 31606 K
incorrect = collect(Gw,w)
incorrect = 
% Expected answer, numerically close, num and den divided by 5
% Manually obtained
correct = (6141*K*w^2 + (12642 - 4924*K)*w - 1217*K + 27358)/(10000*w^2 - 20000*w + 10000);
correct = collect(correct,w)
correct = 
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Cesar Adolfo Cruz Vargaya
Cesar Adolfo Cruz Vargaya 2022-11-1
is there a way to avoid that? Or there is a way to get rid of small values?
Torsten
Torsten 2022-11-1
Sure.
Replace
GzSFDen = 1.0*z^2 + (0.36788*K - 1.3679)*z + 0.26424*K + 0.36788;
by
GzSFDen = 1.0*z^2 + (0.36788*K - 1.36788)*z + 0.26424*K + 0.36788;

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