MATLAB: Not enough input arguments is showing when a simple “fmincon” code is ran, anyone please help

Question

 options = optimoptions('fmincon','Display','iter','Algorithm','sqp');
 fun = @(x)sum((x.*(log(x))));
 A = [];
 b = [];
 lb = [0,0,0,0,0];
 ub = [1,1,1,1,1];
 Aeq = [1,1,1,1,1;0,1,2,3,4];
 beq = [1;3];
 x0 = [.2 .2 .2 .2 .2];
 x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,nonlinfn,options);
 display(x)

where the non linear function is:

 function [c,ceq] = nonlinfn(x)
 c = [];
 ceq = sum(x.*x)-1;

If

 ceq = @(x)sum(x.*x)-1

is used, gives a result but the results is same if we don't use the non linear constraint. Now why arguments are few?

Answer 1

Your error is that your fmincon call uses nonlinfn instead of the function handle @nonlinfn:

x = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,@nonlinfn,options); % this avoids the error

I am afraid that, when I tried running the corrected code, it converged to an infeasible point. Your problem may not be well-formulated. At the least, try giving analytic gradient and maybe Hessian.

Alan Weiss

MATLAB mathematical toolbox documentation