Hi,
The Optimization Toolbox functions, or any other minimization function, should not return any complex solutions. The most common cause of this is that the objective function called by the minimization function returns a complex value. This can occur in several situations, such as when you take the square root of a negative number and/or raise a negative number to a fractional power.
For example, in the following code, where x is a negative number, complex and imaginary solutions will be generated.
>> sqrt(x)
>> x^(1/2)
To avoid these problems, you need to follow either of the two ways:
- Bound your solution so that complex numbers are not generated.
- Adjust the output of your function to ensure that it doesn't produce any complex outputs. To accomplish this bounding, you must investigate what causes your objective function to return complex numbers. It maybe that there are mathematical properties of the function you were not aware of.
Another possible explanation is that bounds need to be set on the acceptable solutions. You can set bounds with most functions in the Optimization Toolbox. For instance, "lsqnonlin" is one such method which allows to specify lower and upper bounds on the variables. You can refer to the following documentation link in order to know more about "lsqnonlin" solver:
I hope this will help.
Regards,
Zuber
