MATLAB: Optimisation toolbox error

optimisation toolbox

I have the following function which I wan to use in optimisation toolbox:
function diff = fit_simp_optim()
% This function is called by lsqnonlin.
% x is a vector which contains the coefficients of the
% equation.  X and Y are the option data sets that were
% passed to lsqnonlin.
X=xlsread('QS2T.xls',9,'V638:C1835');
Y=xlsread('QS2T.xls',9,'W638:W1835');
diff = (A+B*(X.^n)) - Y;
end
Now, in my command window I type:
>>optimtool
I get the optimisation toolbox;
In the optimisation toolbox,
1)corresponding to to the solver i select, lsqnonlin
2)then corresponding to algorithm, I select Trust region reflective
3)then corresponding to objective function i type @fit_simp_optim() which is the name of my .m function file
4)derivatives approximated by solver
5)Start point i give (which is for constants A,B,C- see my function above):[800;1537;0.1448]
6)Lower bound as [800;0;0] and Upper bound as [1600;6000;10]
Howver, when i start, it starts optimising but then says 'too many input arguments'
Please can anyoone help.

Best Answer

The function you pass to lsqnonlin must accept a vector of values the same size as your starting point, and must return a vector of function values (possibly a different size.)
Have another look at your fit_simp_optim code: you use A and B and n but those are not defined as variables anywhere. (What happened to C, by the way?)
Redefine your code:
function diff = fit_simp_optim(ABn, X, Y)
    % This function is called by lsqnonlin.
    % x is a vector which contains the coefficients of the
    % equation.  X and Y are the option data sets that were
    % passed to lsqnonlin.
    A = ABC(1); B = ABC(2); n = ABC(3);
    diff = (A+B*(X.^n)) - Y;
end
Then code
X = xlsread('QS2T.xls',9,'V638:C1835');
Y = xlsread('QS2T.xls',9,'W638:W1835');
lb = [800;0;0];
ub = [1600;600;10];
StartAt = [800;1537;0.1448];
optABn = lsqnonlin( @(ABn) fit_simp_optim(ABn,X,Y), StartAt, lb, ub);
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