MATLAB: Find optimized x1, x2, x3 for a given y.

genetic algorithmmatlab functionoptimization

Hi,

I have a function like below:

y=x1^2+2*x1*x2+x3^2;

I want to find the values for x1, x2 and x3 for y=2.

How can I do that? I tried with genetic algorithm using 'ga' function but looks like that's not the right one. Can anyone please help me how should I approach or is there any built in function to get that? Thanks in advance.

Best Answer

y = 2;
fun = @(x) (x(1).^2 + 2.*x(1).*x(2) + x(3).^2 - y).^2
bestx = ga(fun, 3);
x1 = bestx(1); x2 = bestx(2); x3 = bestx(3);

Note: there are an infinite number of solutions. It does not start to get interesting until you put on constraints.

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There are issues with the definition of 'myfun'. Compare it with the following to see the errors.

function f = myfun(x)
x1 = x(1);
x2 = x(2);
x3 = x(3);
f = (1./(1+(x1-x2).^2)) + sin(0.5*pi.*x2.*x3) + exp(((-x1+x)./x2)-2).^2;
end

MATLAB: How can i fix this error ? Failure in initial user-supplied objective function evaluation. FMINUNC cannot continue.

f=@(x)(1 + (x(1) + x(2) + 1).^2.*(19 - 14*x(1) + 3*x(1).^2 - 14*x(2) + 6*x(1).*x(2) + 3*x(2).^2)).*...  
(30 + (2*x(1) - 3*x(2)).^2.*(18 - 32*x(1) + 12*x(1).^2 + 48*x(2) - 36*x(1).*x(2) + 27*x(2).^2));

Best wishes

Torsten.

Best Answer

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MATLAB: How can i fix this error ? Failure in initial user-supplied objective function evaluation. FMINUNC cannot continue.

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