control.xferfcn._convert_to_transfer_function

control.xferfcn._convert_to_transfer_function(sys, inputs=1, outputs=1, use_prefix_suffix=False)[source]

Convert a system to transfer function form (if needed).

If sys is already a transfer function, then it is returned. If sys is a state space object, then it is converted to a transfer function and returned. If sys is a scalar, then the number of inputs and outputs can be specified manually, as in:

>>> from control.xferfcn import _convert_to_transfer_function
>>> sys = _convert_to_transfer_function(3.) # Assumes inputs = outputs = 1
>>> sys = _convert_to_transfer_function(1., inputs=3, outputs=2)

In the latter example, the matrix transfer function for sys is:

[[1., 1., 1.]
 [1., 1., 1.]].

If sys is an array_like type, then it is converted to a constant-gain transfer function.

Note: no renaming of inputs and outputs is performed; this should be done by the calling function.

Arrays can also be passed as an argument. For example:

sys = _convert_to_transfer_function([[1., 0.], [2., 3.]])

will give a system with numerator matrix [[[1.0], [0.0]], [[2.0], [3.0]]] and denominator matrix [[[1.0], [1.0]], [[1.0], [1.0]]].