ans = 
Force symbolic simplification to eliminate variable
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When breaking down a (long and complex) formula 
into the form 
, I use the approach of the lincoeffs script.
into the form , I use the approach of the lincoeffs script.The problem is, that I still have u in b, because simplification isn't detecting that the terms cancel out.
Is there a trick to force the elimination of u-terms?
The symbolic expression is attached if you want to try it, the code is as follows:
% NOT WORKING - extract coefficients of ddddh_fun
syms u
% ddddh_fun = expand(ddddh_fun);
ddddh_fun_formula = formula(ddddh_fun) == 0;
[ddddh_fun_A,ddddh_fun_b] = lincoeffs(ddddh_fun_formula,u)
ddddh_fun_b = simplify(ddddh_fun_b,'Steps',50);
---
% WORKING - extract coefficients of ddddh_fun
syms u
ddddh_fun = expand(ddddh_fun);
ddddh_fun_formula = formula(ddddh_fun) == 0;
[ddddh_fun_A,ddddh_fun_b] = lincoeffs(ddddh_fun_formula,u)
ddddh_fun_b = simplify(ddddh_fun_b,'Steps',50);
The problem with this is, that the very expanded expression from the working version isn't very readable when I do export is as Latex, which is necessary for me.
To read the symbolic function and the matlabFunction derived from this is also very hard this way.
采纳的回答
Hi ludolfusexe,
load ddddh_fun
symvar(ddddh_fun)
syms u
% A*u = b
[A,b] = equationsToMatrix(ddddh_fun == 0,u)
Verify that A and b do not depend on u
symvar(A)
symvar(b)
Reverse sign of b for desired form: A*u + b = 0
b = -b;
Verify
simplify(ddddh_fun - (A*u + b))
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