python-control
diff --git a/‎README.rst‎
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diff --git a/‎control/config.py‎
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diff --git a/‎control/ctrlutil.py‎
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diff --git a/‎control/freqplot.py‎
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diff --git a/‎control/matlab/wrappers.py‎
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diff --git a/‎control/tests/ctrlutil_test.py‎
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diff --git a/‎control/tests/flatsys_test.py‎
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diff --git a/‎doc/conf.py‎
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@@ -22,14 +22,17 @@ Python Control Systems Library
 The Python Control Systems Library is a Python module that implements basic
 operations for analysis and design of feedback control systems.
 
-
 Have a go now!
-==============
+--------------
 Try out the examples in the examples folder using the binder service.
 
 .. image:: https://mybinder.org/badge_logo.svg
  :target: https://mybinder.org/v2/gh/python-control/python-control/HEAD
 
+The package can also be installed on Google Colab using the commands::
+
+  !pip install control
+  import control as ct
 
 Features
 --------
@@ -44,17 +47,16 @@ Features
 - Nonlinear systems: optimization-based control, describing functions, differential flatness
 
 Links
-=====
+-----
 
 - Project home page: http://python-control.org
 - Source code repository: https://github.com/python-control/python-control
 - Documentation: http://python-control.readthedocs.org/
 - Issue tracker: https://github.com/python-control/python-control/issues
 - Mailing list: http://sourceforge.net/p/python-control/mailman/
 
-
 Dependencies
-============
+------------
 
 The package requires numpy, scipy, and matplotlib.  In addition, some routines
 use a module called slycot, that is a Python wrapper around some FORTRAN
@@ -64,6 +66,7 @@ functionality is limited or absent, and installation of slycot is recommended
 
 https://github.com/python-control/Slycot
 
+
 Installation
 ============
 
@@ -73,7 +76,7 @@ Conda and conda-forge
 The easiest way to get started with the Control Systems library is
 using `Conda <https://conda.io>`_.
 
-The Control Systems library has been packages for the `conda-forge
+The Control Systems library has packages available using the `conda-forge
 <https://conda-forge.org>`_ Conda channel, and as of Slycot version
 0.3.4, binaries for that package are available for 64-bit Windows,
 OSX, and Linux.
@@ -83,6 +86,10 @@ conda environment, run::
 
   conda install -c conda-forge control slycot
 
+Mixing packages from conda-forge and the default conda channel can
+sometimes cause problems with dependencies, so it is usually best to
+instally NumPy, SciPy, and Matplotlib from conda-forge as well.
+
 Pip
 ---
 
@@ -92,7 +99,8 @@ To install using pip::
   pip install control
 
 If you install Slycot using pip you'll need a development environment
-(e.g., Python development files, C and Fortran compilers).
+(e.g., Python development files, C and Fortran compilers).  Pip
+installation can be particularly complicated for Windows.
 
 Installing from source
 ----------------------
@@ -106,11 +114,13 @@ toplevel `python-control` directory::
 Article and Citation Information
 ================================
 
-An `article <https://ieeexplore.ieee.org/abstract/document/9683368>`_ about the library is available on IEEE Explore. If the Python Control Systems Library helped you in your research, please cite::
+An `article <https://ieeexplore.ieee.org/abstract/document/9683368>`_ about
+the library is available on IEEE Explore. If the Python Control Systems Library helped you in your research, please cite::
 
   @inproceedings{python-control2021,
     title={The Python Control Systems Library (python-control)},
-    author={Fuller, Sawyer and Greiner, Ben and Moore, Jason and Murray, Richard and van Paassen, Ren{\'e} and Yorke, Rory},
+    author={Fuller, Sawyer and Greiner, Ben and Moore, Jason and
+            Murray, Richard and van Paassen, Ren{\'e} and Yorke, Rory},
     booktitle={60th IEEE Conference on Decision and Control (CDC)},
     pages={4875--4881},
     year={2021},
 
@@ -76,7 +76,6 @@ def set_defaults(module, **keywords):
     >>> ct.defaults['freqplot.number_of_samples']
     100
     >>> # do some customized freqplotting
-    >>> ct.reset_defaults()
 
     """
     if not isinstance(module, str):
@@ -209,7 +208,6 @@ def use_matlab_defaults():
     --------
     >>> ct.use_matlab_defaults()
     >>> # do some matlab style plotting
-    >>> ct.reset_defaults()
 
     """
     set_defaults('freqplot', dB=True, deg=True, Hz=False, grid=True)
@@ -229,7 +227,6 @@ def use_fbs_defaults():
     --------
     >>> ct.use_fbs_defaults()
     >>> # do some FBS style plotting
-    >>> ct.reset_defaults()
 
     """
     set_defaults('freqplot', dB=False, deg=True, Hz=False, grid=False)
@@ -263,7 +260,6 @@ class and functions.  If flat is `False`, then matrices are
     --------
     >>> ct.use_numpy_matrix(True, False)
     >>> # do some legacy calculations using np.matrix
-    >>> ct.reset_defaults()
 
     """
     if flag and warn:
@@ -285,7 +281,6 @@ def use_legacy_defaults(version):
     >>> ct.use_legacy_defaults("0.9.0")
     (0, 9, 0)
     >>> # do some legacy style plotting
-    >>> ct.reset_defaults()
 
     """
     import re
 
@@ -44,6 +44,7 @@
 from . import lti
 import numpy as np
 import math
+import warnings
 
 __all__ = ['unwrap', 'issys', 'db2mag', 'mag2db']
 
@@ -99,6 +100,8 @@ def issys(obj):
     False
 
     """
+    warnings.warn("issys() is deprecated; use isinstance(obj, ct.LTI)",
+                  FutureWarning, stacklevel=2)
     return isinstance(obj, lti.LTI)
 
 def db2mag(db):
 
@@ -558,21 +558,21 @@ def nyquist_plot(
         List of linear input/output systems (single system is OK). Nyquist
         curves for each system are plotted on the same graph.
 
-    plot : boolean
-        If True, plot magnitude
-
-    omega : array_like
+    omega : array_like, optional
         Set of frequencies to be evaluated, in rad/sec.
 
-    omega_limits : array_like of two values
+    omega_limits : array_like of two values, optional
         Limits to the range of frequencies. Ignored if omega is provided, and
         auto-generated if omitted.
 
-    omega_num : int
+    omega_num : int, optional
         Number of frequency samples to plot.  Defaults to
         config.defaults['freqplot.number_of_samples'].
 
-    color : string
+    plot : boolean, optional
+        If True (default), plot the Nyquist plot.
+
+    color : string, optional
         Used to specify the color of the line and arrowhead.
 
     return_contour : bool, optional
@@ -690,6 +690,13 @@ def nyquist_plot(
        to `none` will turn off indentation.  If `return_contour` is True, the
        exact contour used for evaluation is returned.
 
+    3. For those portions of the Nyquist plot in which the contour is
+       indented to avoid poles, resuling in a scaling of the Nyquist plot,
+       the line styles are according to the settings of the `primary_style`
+       and `mirror_style` keywords.  By default the scaled portions of the
+       primary curve use a dotted line style and the scaled portion of the
+       mirror image use a dashdot line style.
+
     Examples
     --------
     >>> G = ct.zpk([], [-1, -2, -3], gain=100)
 
@@ -5,7 +5,7 @@
 import numpy as np
 from ..iosys import ss
 from ..xferfcn import tf
-from ..ctrlutil import issys
+from ..lti import LTI
 from ..exception import ControlArgument
 from scipy.signal import zpk2tf
 from warnings import warn
@@ -124,7 +124,7 @@ def _parse_freqplot_args(*args):
     i = 0
     while i < len(args):
         # Check to see if this is a system of some sort
-        if issys(args[i]):
+        if isinstance(args[i], LTI):
             # Append the system to our list of systems
             syslist.append(args[i])
             i += 1
 
@@ -1,7 +1,8 @@
 """ctrlutil_test.py"""
 
 import numpy as np
-
+import pytest
+import control as ct
 from control.ctrlutil import db2mag, mag2db, unwrap
 
 class TestUtils:
@@ -58,3 +59,8 @@ def test_mag2db(self):
     def test_mag2db_array(self):
         db_array = mag2db(self.mag)
         np.testing.assert_array_almost_equal(db_array, self.db)
+
+    def test_issys(self):
+        sys = ct.rss(2, 1, 1)
+        with pytest.warns(FutureWarning, match="deprecated; use isinstance"):
+            ct.issys(sys)
@@ -212,7 +212,7 @@ def test_kinematic_car_ocp(
             elif re.match("Iteration limit.*", traj_ocp.message) and \
                  re.match(
                      "conda ubuntu-3.* Generic", os.getenv('JOBNAME', '')) and \
-                 re.match("1.24.[01]", np.__version__):
+                 re.match("1.24.[012]", np.__version__):
                 pytest.xfail("gh820: iteration limit exceeded")
 
             else:
 
@@ -37,11 +37,12 @@
 import re
 import control
 
+# Get the version number for this commmit (including alpha/beta/rc tags)
+release = re.sub('^v', '', os.popen('git describe').read().strip())
+
 # The short X.Y.Z version
-version = re.sub(r'(\d+\.\d+\.\d+)(.*)', r'\1', control.__version__)
+version = re.sub(r'(\d+\.\d+\.\d+(.post\d+)?)(.*)', r'\1', release)
 
-# The full version, including alpha/beta/rc tags
-release = control.__version__
 print("version %s, release %s" % (version, release))
 
 # -- General configuration ---------------------------------------------------
@@ -206,11 +207,10 @@ def linkcode_resolve(domain, info):
         linespec = ""
 
     base_url = "https://github.com/python-control/python-control/blob/"
-    if 'dev' in control.__version__:
+    if release != version:      # development release
         return base_url + "main/control/%s%s" % (fn, linespec)
-    else:
-        return base_url + "%s/control/%s%s" % (
-           control.__version__, fn, linespec)
+    else:                       # specific version
+        return base_url + "%s/control/%s%s" % (version, fn, linespec)
 
 # Don't automaticall show all members of class in Methods & Attributes section
 numpydoc_show_class_members = False
@@ -282,4 +282,5 @@ def linkcode_resolve(domain, info):
 import control as ct
 import control.optimal as obc
 import control.flatsys as fs
+ct.reset_defaults()
 """