Error happen when doing optimization by using "surrogateopt"

I am trying to do optimization by using "surrogateopt" function.

I got an error "Objective function must return a scalar value".

And I couldn't find the problem.

clear
close all
clc
h = 0.01;
t = 0:h:10;
x = [0 0]';

for i = 1:1001
    x1(i) = x(1);
    x2(i) = x(2);
    
    if x1(i) >0
        a = pi/3;
    elseif x1(i)<=0
        a = -pi/3;
    end
    
    A = [cos(a) sin(a);
        sin(a) cos(a)];
    B = [0 1]';
    
   intcon = 1;

    lb = -1;
    ub = 1;
    obj =@(u) fun(A, x, B, u);
    u = surrogateopt(obj, lb, ub, intcon);

    x = fun(A, x, B, u);
    
end

figure
plot(x1, x2)
grid on

function f1 = fun(A, x, B, u)
    f1 = 0.8*A*x+B*u;
end

Answer 1

[Stephan]

f1 is a 2x1 vector - the objective of an optimization has to be a scalar. Thats the error. You need a criterion that expresses the success of your optimization as a scalar.