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Implement missing type conversions for block diagram algebra #513
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(this was originally its own issue, #541, but I copied the comment into here and closed that issue to keep discussion about its possible implementation in this more general thread.)
The following code causes a bug when it tries to raise an error:
import control as ct import control.iosys as io 2*io.ss2io(ct.ss(1,1,1,1))
raise NotImplemented("Scalar multiplication not yet implemented")This is because
InputOutputSystemsdefine various methods, e.g.__mul__that override those inStateSpaceand some are not implemented yet.Options that come to mind if we want this to work better:
- Test for instances of
StateSpacecorrectly and dispatch. This seems to be onerous and at odds with how inheritance ought to make things easier. - In the
__init__method ofLinearIOSystem, delete those methods - move those operations to NonLinearIOSystem (and override as necessary in
LinearIOSystemwhen it makes sense to create a newLinearICSystem)
Related: many of the methods like
__mul__don't act onselfandotherbut rathersys1andsys2. This might still work, but I think the first argument should beselfaccording to Python convention.- Test for instances of
A number of these conversions have been implemented in #672. Leaving this issue open since there are still a few cases that aren't handled (see table in tests/type_conversion_test.py).
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 in control/tests/type_conversion_test.py.
A few of the more useful ones:
StateSpaceobjects 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.FrequencyResponseDataandInputOutputSystemobjects should be able to interact with floats and arrays.InputOutputSystemobjects should be able to interact withLTIsystems by converting the LTI system into aLinearIOSystem.FrequencyResponseDatasystems should be able to be combined withStateSpaceandTransferFunctionoptions by evaluating the state space system or transfer function at the FRD frequencies.