add documentation on __call__ functions

murrayrm · murrayrm · commit 4e066703c251 · 2025-02-02T20:39:22.000-08:00
diff --git a/control/flatsys/basis.py b/control/flatsys/basis.py
@@ -71,11 +71,11 @@ def __repr__(self):
             f'N={self.N}>'
 
     def __call__(self, i, t, var=None):
-        """Evaluate the ith basis function at a point in time"""
+        """Evaluate the ith basis function at a point in time."""
         return self.eval_deriv(i, 0, t, var=var)
 
     def var_ncoefs(self, var):
-        """Get the number of coefficients for a variable"""
+        """Get the number of coefficients for a variable."""
         return self.N if self.nvars is None else self.coef_length[var]
 
     def eval(self, coeffs, tlist, var=None):
diff --git a/control/frdata.py b/control/frdata.py
@@ -130,7 +130,7 @@ class constructor, using the :func:`~control.frd` factory function, or
 
     A frequency response data object is callable and returns the value of the
     transfer function evaluated at a point in the complex plane (must be on
-    the imaginary access).  See :meth:`~control.FrequencyResponseData.__call__`
+    the imaginary axis).  See :meth:`~control.FrequencyResponseData.__call__`
     for a more detailed description.
 
     A state space system is callable and returns the value of the transfer
diff --git a/control/nlsys.py b/control/nlsys.py
@@ -163,7 +163,7 @@ def __str__(self):
 
     # Return the value of a static nonlinear system
     def __call__(sys, u, params=None, squeeze=None):
-        """Evaluate a (static) nonlinearity at a given input value
+        """Evaluate a (static) nonlinearity at a given input value.
 
         If a nonlinear I/O system has no internal state, then evaluating the
         system at an input `u` gives the output `y = F(u)`, determined by the
diff --git a/control/xferfcn.py b/control/xferfcn.py
@@ -331,7 +331,6 @@ def den_list(self):
     num, den = num_list, den_list
 
     def __call__(self, x, squeeze=None, warn_infinite=True):
-
         """Evaluate system's transfer function at complex frequencies.
 
         Returns the complex frequency response `sys(x)` where `x` is `s` for
diff --git a/doc/classes.rst b/doc/classes.rst
@@ -1,6 +1,7 @@
-.. _class-ref:
 .. currentmodule:: control
 
+.. _class-ref:
+
 **********************
 Control system classes
 **********************
diff --git a/doc/descfcn.rst b/doc/descfcn.rst
@@ -26,7 +26,8 @@ If such an intersection exists, it indicates that there may be a limit
 cycle of amplitude :math:`A` with frequency :math:`\omega`.
 
 Describing function analysis is a simple method, but it is approximate
-because it assumes that higher harmonics can be neglected. 
+because it assumes that higher harmonics can be neglected.
+
 
 Module usage
 ------------
@@ -90,3 +91,5 @@ Module classes and functions
    friction_backlash_nonlinearity
    relay_hysteresis_nonlinearity
    saturation_nonlinearity
+   ~DescribingFunctionNonlinearity.__call__
+
diff --git a/doc/examples.rst b/doc/examples.rst
@@ -1,6 +1,7 @@
-.. _examples:
 .. currentmodule:: control
 
+.. _examples:
+
 ********
 Examples
 ********
diff --git a/doc/iosys.rst b/doc/iosys.rst
@@ -1,7 +1,7 @@
-.. _iosys-module:
-
 .. currentmodule:: control
 
+.. _iosys-module:
+
 **************************
 Interconnected I/O Systems
 **************************
diff --git a/doc/linear.rst b/doc/linear.rst
@@ -114,6 +114,11 @@ complicated transfer functions::
 
   sys = 5 * (s + 10)/(s**2 + 2*s + 1)
 
+Transfer functions can be evaluated at a point in the complex plane by
+calling the transfer function object::
+
+  val = sys(s)
+
 Discrete time transfer functions (described in more detail below) can
 be created using `z = ct.tf('z')`.
 
@@ -227,6 +232,7 @@ response.
 
 .. _discrete_time_systems:
 
+
 Discrete time systems
 =====================
 
@@ -275,6 +281,7 @@ including functions for converting between state space and frequency
 domain, sampling systems in time and frequency domain, and creating
 reduced order models.
 
+
 Conversion between representations
 ----------------------------------
 
@@ -382,6 +389,7 @@ purpose, although in that case the output is usually used for plotting
 the frequency response, as described in more detail in the
 :ref:`frequency_response` section.
 
+
 Model reduction
 ---------------
 
diff --git a/doc/nlsys.rst b/doc/nlsys.rst
@@ -1,4 +1,4 @@
-..currentmodule control
+.. currentmodule:: control
 
 Nonlinear system models
 =======================
@@ -111,7 +111,7 @@ Operating points and linearization
 ----------------------------------
 
 A nonlinear input/output system can be linearized around an equilibrium point
-to obtain a :class:`~control.StateSpace` linear system::
+to obtain a :class:`StateSpace` linear system::
 
   sys_ss = ct.linearize(sys_nl, xeq, ueq)
 
@@ -143,7 +143,7 @@ Simulations and plotting
 ------------------------
 
 To simulate an input/output system, use the
-:func:`~control.input_output_response` function::
+:func:`input_output_response` function::
 
   resp = ct.input_output_response(io_sys, T, U, x0, params)
   t, y, x = resp.time, resp.outputs, resp.states
@@ -159,3 +159,32 @@ different plot elements. The :func:`combine_time_responses` function
 an be used to combine multiple time responses into a single
 `TimeResponseData` object.  See the :ref:`response-chapter` chapter
 for more information on this functionality.
+
+Nonlinear system properties
+---------------------------
+
+The following basic attributes and methods are available for
+:class:`NonlinearIOSystem` objects:
+
+.. autosummary::
+
+   ~NonlinearIOSystem.dynamics
+   ~NonlinearIOSystem.output
+   ~NonlinearIOSystem.linearize
+   ~NonlinearIOSystem.__call__
+
+The :func:`~NonlinearIOSystem.dynamics` method returns the right hand
+side of the differential or difference equation, evaluated at the
+current time, state, input, and (optionally) parameter values.  The
+:func:`~NonlinearIOSystem.output` method returns the system output.
+For static nonlinear systems, it is also possible to obtain the value
+of the output by directly calling the system with the value of the
+input::
+
+  >>> sys = ct.nlsys(
+  ...    None, lambda t, x, u, params: np.sin(u), inputs=1, outputs=1)
+  >>> sys(1)
+  np.float64(0.8414709848078965)
+
+The :func:`~NonlinearIOSystem.linearize` method is equivalent to the
+:func:`linearize` function.
diff --git a/doc/statesp.rst b/doc/statesp.rst
@@ -31,6 +31,7 @@ The following basic attributes and methods are available for
    ~StateSpace.dcgain
    ~StateSpace.sample
    ~StateSpace.returnScipySignalLTI
+   ~StateSpace.__call__
 
 A complete list of attributes, methods, and properties is available in
 the :class:`StateSpace` class documentation.
diff --git a/doc/xferfcn.rst b/doc/xferfcn.rst
@@ -19,6 +19,7 @@ The following basic attributes and methods are available for
    ~TransferFunction.dcgain
    ~TransferFunction.sample
    ~TransferFunction.returnScipySignalLTI
+   ~TransferFunction.__call__
 
 A complete list of attributes, methods, and properties is available in
 the :class:`TransferFunction` class documentation.
