how to run the function "fminunc" correctly

I got a error message when I try to use the function "fminunc" to optimize the weights of a neural network. At the beginning, I thought it was caused by some tricks of the back-propagation algorithm, So I changed a simple case as follows:

A simple .m file:

function [f,g] = myfun(x)
f = 3*x(1)^2 + 2*x(1)*x(2) + x(2)^2;    % Cost function
if nargout > 1
   g(1) = 6*x(1)+2*x(2);
   g(2) = 2*x(1)+2*x(2);
end

and run the following commands:

options = optimoptions('fminunc','GradObj','on','Algorithm','trust-region');
x0 = [1,1];
[x,fval] = fminunc(@myfun,x0,options);

it causes error like follows:

Error using color
Too many input arguments.

Error in sfminbx (line 150)
    group = color(Hstr,p);

Error in fminunc (line 450)
   [x,FVAL,~,EXITFLAG,OUTPUT,GRAD,HESSIAN] = sfminbx(funfcn,x,l,u, ...|

I tried the same code in Matlab 2014b and Matlab 2013 and got the same error. I also tried to replace the function "optimoptions" with "optimset" but it didn't work. I noticed that the the function "color" that provided by MATLAB only allows one input argument. However, the default function "color" is used to change the color of a plot handler and it apparently has nothing to do with the function "color" in the function "sfminbx". However I didn't find any other .m files named by "color" in the root directory and its subfolders.

So I am totally confused about this error. Any one can help me? Thank you very much!

Answer 1

[Walter Roberson]

which -all color
which -all sfminbx

If one of the two comes up first with a routine that is not supplied by Mathworks then remove that routine (or take its directory out of your MATLAB path).