As described in issue#459 and PR#498, there are a number of type conversions for various overloaded operators that are not yet implemented. A table of the current and desired operations can be found incontrol/tests/type_conversion_test.py.

A few of the more useful ones:

• SISOStateSpace objects should be allowed to serve as a quotient under appropriate circumstances (so that you can write things likeT = P*C/(1 + P*C) with state space objects, as you currently can with transfer functions.
• FrequencyResponseData andInputOutputSystem objects should be able to interact with floats and arrays.
• InputOutputSystem objects should be able to interact withLTI systems by converting the LTI system into aLinearIOSystem.
• FrequencyResponseData systems should be able to be combined withStateSpace andTransferFunction options by evaluating the state space system or transfer function at the FRD frequencies.