MATLAB Pole Command
From ControlTheoryPro.com

1 Introduction to MATLAB's pole command
The pole command computes the poles of an LTI model whether that model is SISO or MIMO.
2 Usage
The pole command is a simple one. There is only 1 usage of it:
>> p = pole(sys);
This will return the poles of the LTI model sys. It doesn't matter if sys is a State Space object, Transfer Function, ZeroPoleGain model, or FRD (typically used fo rmeasured data).
3 Notes
 This function requires the Control System Toolbox.
4 Warnings
The function will not necessarily compute multiple poles accurately. In other words if you have 2 or more poles at the poles may appear as a circular cluster of poles centered at with a radius on the order of

 where
 is the machine precision (eps) and
 is the number of poles at .
 where