As an example for doing this, I give you an example. Define a function as follows:
function er = objfun(a)
global y x
z=a;
z(4)=z(2)*z(3)/z(1);
er=sum((y-x*z).^2);
end
then type in the command window the following:
global y x
% input data:
% y=sort(rand(5,1));
% x1=sort(rand(5,1));
% x2=sort(10*rand(5,1));
% x3=sort(100*rand(5,1));
% x4=sort(1000*rand(5,1));
% ainit=[0.5;0.8;0.1];
x=[x1 x2 x3 x4];
fmincon(@objfun,ainit,ones(1,3),Inf)
