using fmincon for min problem with nonlinear constraints

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Hello,

I tried to solve a min problem with nonlinear constraints with fmincon, but I always get an error massage.

Here are the functions I use:

function[F]= KalibrierungCIR(x)
h=sqrt(x(1)^2+2*x(3)^2); 
A=(((2*h*exp(x(1)+h)*Maturity/2))./(2*h+(x(1)+h)*(exp(Maturity*h)-1))).^(2*x(1)*x(2)/x(3)^2); 
B=(2*(exp(Maturity*h)-1))./(2*h+(x(1)+h)*(exp(Maturity*h)-1)); 
PCIR=A.*exp(-B.*x(4));
lambda_Dach=-(log(PCIR(2:length(PCIR)))-log(PCIR(1:length(PCIR)-1)))./ (Maturity(2:length(Maturity))-Maturity(1:length(Maturity)-1));
F=sum(lambda_Dach-lambda)/length(lambda);

Hier i get a scalar. My constraints are:

function [c] = mycon(x)
c = [x(3)^2-2*x(2)*x(1)]; 
ceq=[];

Then I type:

lb=[0.00000001 0.00000001 0.0000001 0.0001]; x0=[0.1 0.1 0.1 0.1]; [x,fval]=fmincon(@KalibrierungCIR,x0,[],[],[],[],lb,[],@myfun)

and get the error message:

Error using feval Undefined function 'myfun' for input arguments of type 'double'.
Error in fmincon (line 681) [ctmp,ceqtmp] = feval(confcn{3},X,varargin{:});
Caused by: Failure in initial user-supplied nonlinear constraint function evaluation. FMINCON cannot continue.

I have realy no idea where the problem is! I would be very greatful if someone could help me.