CODEWITHSUNDEEP
matlab
user1068636
user1068636

Reputation: 1939

How do you solve a system of nonlinear equations in matlab?

I am trying to use MATLAB to find critical values of 

f(x,y) = (y-2)ln(xy)

diff(f,x) = (y - 2)/x = 0
diff(f,y) = log(x*y) + (y - 2)/y = 0

Solving the above 2 equations and 2 unknowns by hand, I get x = 1/2 and y = 2. But how do I get MATLAB to yield this result?

I know I have to either use fsolve or fzero but I'm not sure how to.

Upvotes: 0

Views: 69

Answers (1)

Matthew Gunn
Matthew Gunn

Reputation: 4519

If you REALLY want to solve that with fsolve, you could do:

o = optimoptions('fsolve','MaxFunEvals',1e5,'MaxIter',1e5);

x0 = [.9;2.1]; % Note this IS SENSITIVE to the starting location!

f = @(x) [(x(2) - 2) / x(1); log(x(2)) + log(x(1)) + 1 - 2/x(2)];
x = fsolve(f,x0, o)

Upvotes: 1

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