Find minimum of multi-variable function on fixed interval with additional parameter inputs

Hello all,

I would like to find the minimum of a family of functions on a fixed interval.

function yx = test_function(x,xin2)
    a=xin2(1);
    b=xin2(2);
    c=xin2(3);
    yx = abs((x(1)*x(2))/4 + ((x(1)^2*x(2)^2)/a + (x(1)*x(2))/b - 1/4)^(c) + 1/2)+x(3);

Thus, I would like to find the minimum of yx (which is determined by x(1), x(2) and x(3)) for a given set of values for a,b,c.

As I would like to repeat this exercise for a large number of combinations of a,b,c I would like to be able to change these automatically in a loop.

xin2=[16,4,1/2];
lb = [0 0 0];
ub = [1 1 1];
f=@test_function;

[x, fval] = fmincon(f(x,xin2), [rand(), rand(), rand()], A, b, Aeq, Beq, lb, ub)

The error message I get:

Error using optimfcnchk (line 101)
FUN must be a function, a valid character vector expression, or an inline function object.

Error in fmincon (line 415)
   funfcn = optimfcnchk(FUN,'fmincon',length(varargin),funValCheck,flags.grad,flags.hess,false,Algorithm);

Error in Untitled2 (line 51)
[x, fval] = fmincon(f(x,xin2), [rand(), rand(), rand()], A, b, Aeq, Beq, lb, ub)

Can someone help me?

Kind regadrs,

Tom

Answer 1

[Alan Weiss]

You need to pass the parameters correctly. See Passing Extra Parameters. In your case, you need to either nest the function in a function that changes the parameters, or recreate an anonymous function each time, something like

xin = [16 4 1/2];
f = @(x)test_function(x,xin);
[x, fval] = fmincon(f, rand(1,3), A, b, Aeq, Beq, lb, ub)

Alan Weiss

MATLAB mathematical toolbox documentation