Why i am getting Error in matlab fmincon function? - matlab

Question

I am not good at Matlab at all. I am trying to find minimum of function witjh constrains.
I am trying to use eample line by line as it is in documentation (https://www.mathworks.com/help/optim/ug/optimization-toolbox-tutorial.html - part Constrained Optimization Example: User-Supplied Gradients)
I have tried following code:
f = #(x,y) x.*exp(-x.^2-y.^2)+(x.^2+y.^2)/20;
g = #(x,y) x.*y/2+(x-2).^2+(y-2).^2/2-4;
x0 = [2 ,0];
options = optimoptions('fmincon','Algorithm','interior-point','Display','iter');
gfun = #(x,y) deal(g(x,y),[]);
[x,fval,exitflag,output] = fmincon(f,x0,[],[],[],[],[],[],gfun,options);
And this is the console output:
>> Untitled4
Not enough input arguments.
Error in Untitled4>#(x,y)x.*exp(-x.^2-y.^2)+(x.^2+y.^2)/20 (line 1)
f = #(x,y) x.*exp(-x.^2-y.^2)+(x.^2+y.^2)/20;
Error in fmincon (line 552)
initVals.f = feval(funfcn{3},X,varargin{:});
Error in Untitled4 (line 7)
[x,fval,exitflag,output] = fmincon(f,x0,[],[],[],[],[],[],gfun,options);
Caused by:
Failure in initial objective function evaluation. FMINCON cannot continue.
I don't understand - what is wrong with my function?

Answer 1

you missed the part in the documentation defining fun,
and you miss-defined gfun.
(it is important that both are functions of a single variable, x)
Here is working code:
f = #(x,y) x.*exp(-x.^2-y.^2)+(x.^2+y.^2)/20;
g = #(x,y) x.*y/2+(x-2).^2+(y-2).^2/2-4;
x0 = [2 0];
options = optimoptions('fmincon','Algorithm','interior-point','Display','iter');
fun = #(x) f(x(1),x(2));
gfun = #(x) deal(g(x(1),x(2)),[]);
[x,fval,exitflag,output] = fmincon(fun,x0,[],[],[],[],[],[],gfun,options);