Solving system of 9 nonlinear equaitons in 16 variables
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I have a system of equations as follows:
I am not able to use fsolve as it says in the documentaiton that the number of variables should be as same as the number of equations. I found this on the MathWorks which says that it can be done with fsolve. Please let me know if it can be solved by any other method or by using fsolve. It will also suffice if I can know the solution exists.
I am writing the MATLAB code that I have written using fsolve.
f = @(x) [x(1)*x(9) + x(2)*x(12) + x(3)*x(15) - 13;
x(1)*x(10) + x(2)*x(13) + x(3)*x(16) - 15;
x(1)*x(11) + x(2)*x(14) - x(3)*(x(9) + x(13)) + 1;
x(4)*x(9) + x(5)*x(12) + x(6)*x(15) - 9;
x(4)*x(10) + x(5)*x(13) + x(6)*x(16) - 24;
x(4)*x(11) + x(5)*x(14) - x(6)*(x(9) + x(13));
x(7)*x(9) + x(8)*x(12) - x(15)*(x(1) + x(5)) - 7;
x(7)*x(10) + x(8)*x(13) - x(16)*(x(1) + x(5)) -2;
x(7)*x(11) + x(8)*x(14) + (x(1)+x(5))*(x(9)+x(13)) - 35];
A = zeros(1,9);
fsolve(f, A)
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Accepted Answer
Torsten
on 28 Nov 2022
x0 = -10*ones(16,1);
AB = [13 15 -1;9 24 0;7 2 35];
options = optimset('TolFun',1e-16,'TolX',1e-16);
x = fmincon(@(x)fun(x,AB),x0,[],[],[],[],[],[],[],options);
A = [x(1) x(2) x(3);x(4) x(5) x(6);x(7) x(8) -(x(1)+x(5))]
B = [x(9) x(10) x(11);x(12) x(13) x(14);x(15) x(16) -(x(9)+x(13))]
A*B-AB
function obj = fun(x,AB)
A = [x(1) x(2) x(3);x(4) x(5) x(6);x(7) x(8) -(x(1)+x(5))];
B = [x(9) x(10) x(11);x(12) x(13) x(14);x(15) x(16) -(x(9)+x(13))];
M = A*B - AB;
M = M(:);
obj = sum(M.^2);
end
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