Control

This release introduces several new features as well as bug fixes and documentation improvements:
* Improved default time vector for time response functions (bnavigator, sawyerbfuller)
* New `use_legacy_defaults` function to allow compatibility with previous versions (sawyerbfuller)
* Allow creation of non-proper transfer functions (bnavigator, rlegnain)
* Added ability to set arrow head length and width option in `nyquist_plot` (geekonloose)
* Added ability to 'prewarp' the conversion of continuous to discrete-time systems (sawyerbfuller)
* Added rlocus capability for discrete-time systems (sawyerbfuller)
* Updated `pzmap` grid to be compatible with `matplotlib` updates (bnavigator)
* Implement loadable string representation (__repr__) for tf, ss, and frd (repagh)
* Fixed `margin` computation for discrete time systems (bnavigator)
* Fixed indexing bug in `bdalg.connect` (sawyerbfuller)
* Fixed `InterconnectedSystem` naming bugs, improved conventions (samlaf)
* Fixed `LinearIOSystem` output bug in output function (francescoseccamonte)
* Fixed bug in `forced_response` that overrode `squeeze` parameter (bnavigator)
* Use rad/sec for Bode plot in MATLAB bode (was erroneously defaulting to Hertz) (paulvicioso)
* Removed deprecated `scipy` calls and updated to latest `numpy` (bnavigator)
* Multiple documentation updates (bnavigator, laurensvalk)
* New and improved examples for sisotool, pvtol (repagh, samlaf)
* The `rlocus` function no longer automatically creates a new figure
* Updated unit tests + switch to pytest (bnavigator, sawyerbfuller)
* Return type for eigenvalues in `lqe` changed to 1D array (matches `lqr`)
* Small fixes + documentation updates to `markov`

More info:
* Full list of [merged pull requests](https://github.com/python-control/python-control/pulls?utf8=✓&q=is%3Amerged+milestone%3A0.8.4) associated with this release.
* Full list of [commits](https://github.com/python-control/python-control/compare/0.8.3..0.8.4) associated with this release

This release introduces several new features as well as bug fixes and documentation improvements:

* New input/output systems module for creating nonlinear systems from individual I/O subsystems, with `find_eqpt`, `input_output_response`, and `linearize` functionality
* Initial implementation of differential flatness module for computing feasible trajectories for differentially flat (nonlinear) systems
* Preliminary version of lqe function (sawyerbfuller)
* New dict-based implementation of user-configurable package/module configuration parameters
* Added similarity transformation function
* Add 's' and 'z' variable support to tf()
* Fixed discrete time simulation time step issue
* Reordered Gang of Four plots to match FBS
* Check for symmetric matrices with machine precision (bnavigator)
* Changed root precision tolerance and imaginary detection in `xferfcn._common_den` (bnavigator)
* Fixed bug in timeresp.forced_response (adm78)
* Improved latex representation for exp format and multi-digit exponents of s or z (bnavigator)
* Renamed `FRD` class name `FrequencyResponseData` to fix MacOS sphinx build problems (`FRD` still defined for backward compatibility`
* Allow np.array or np.matrix for state space matrices, operations via `use_numpy_matrix`
* Improved detection of when to add additional points in `root_locus`
* Adaptive gain click criterion and zoom bug fix for `root_locus` (icam0)
* Improved code for ctrb and obsv (billtubbs)
* Documentation updates (bnavigator, murrayrm, roryyorke)
* Updated examples to be PEP compliant
* Improved unit tests (bnavigator, murrayrm), increased coverage to ~80%

More info:
* Full list of [merged pull requests](https://github.com/python-control/python-control/pulls?utf8=✓&q=is%3Amerged+milestone%3A0.8.3+is%3Apr+) associated with this release.
* Full list of [commits](https://github.com/python-control/python-control/compare/0.8.2..master) associated with this release

This is mainly a maintenance release with lots of small bug fixes and performance improvements:

* Fixed a number of small bugs , including discrete time simulations (bnavigator), integer values in state space matrics (don4get), missing zeros on pole/zero plots (Sup3rGeo)

* First cut at a new step_info() function, similar to MATLAB (joaoantoniocardoso)

* Added a new function for dynamically setting gain in sisotool (icam0)

* Anti-stabilizing solutions for Riccati equations are now available (dbacc)

* Printout out state space systems in Jupyter notebooks now formats using LaTeX (alchemyst)

* Additional performance and visualiation improvements: _remove_useless_states (adm78), margins on Bode plots ( icam0), improved damping lines in discrete pzmap (Sup3rGeo)

This release fixes a number of small issues and adds a few new figures:

* A new canonical function `modal_form` can be used to convert a state space system to modal form (ipa-lth)
* Improved pole placement algorithm `place_varga` (rabraker)
* Bug fix in computing poles of MIMO transfer functions
* Indexing of MIMO transfer functions (hungpham2511)
* Additional small bug fixes (adm78, stertingen)
* Documentation updates and fixes (joaoantoniocardoso)
* [List of all changes in this release](https://github.com/python-control/python-control/compare/0.8.0...0.8.1)

* Updated and corrected docstrings ([PR 198](https://github.com/python-control/python-control/pull/198), [PR #216](https://github.com/python-control/python-control/pull/216))
* Better support for MIMO systems in `pole()` and `zero()` functions ([PR 205](https://github.com/python-control/python-control/pull/205), [PR #206](https://github.com/python-control/python-control/pull/206))
* Support for SciPy-1.0.0 updates to the `scipy.signal` module that is used for some python-control functions and support for `numpy` data types (int32, int64, etc) in all python-control functions ([PR 170](https://github.com/python-control/python-control/pull/170))
* Support for static gains (0D state space systems and constant transfer functions) ([PR 104](https://github.com/python-control/python-control/pull/104), [PR #110](https://github.com/python-control/python-control/pull/110), [PR #126](https://github.com/python-control/python-control/pull/126), [PR #129](https://github.com/python-control/python-control/pull/129), [PR #145](https://github.com/python-control/python-control/pull/145))
* Note: Open issues related to this: [165](https://github.com/python-control/python-control/issues/165)
* New functions `obsv` (observable canonical form, [PR 103](https://github.com/python-control/python-control/pull/103)), `augw` and `mixsyn` (mixed sensitivity synthesis, [PR #151](https://github.com/python-control/python-control/pull/151))
* List of merged [pull requests](https://github.com/python-control/python-control/pulls?q=is%3Amerged+milestone%3A0.8.0+is%3Apr) associated with this release.
* List of open [pull requests](https://github.com/python-control/python-control/pulls?q=is%3Aopen+milestone%3A0.8.0+is%3Apr) associated with this release.
* List of [commits](https://github.com/python-control/python-control/compare/v0.7.0...0.8.0) associated with this release

This release updates the build system to be compatible with scikit-build 0.17. We also updated the SLICOT Fortran sources to *5.8 Update 1*.

Relevant changes from the *SLICOT 5.8 Update 1* release notes

**`MB03VY:`** Set `A( ILO, ILO, J )` to 1 if `IHI = ILO` in the loop labelled 20.

What's Changed
* update workflow to pass jobname to python-control pytest by murrayrm in https://github.com/python-control/Slycot/pull/190
* Add lower numpy bound by bnavigator in https://github.com/python-control/Slycot/pull/192
* Don't include package data by bnavigator in https://github.com/python-control/Slycot/pull/194
* Update SLICOT to 5.8 Update 1 by bnavigator in https://github.com/python-control/Slycot/pull/195

**Full Changelog**: https://github.com/python-control/Slycot/compare/v0.5.3...v0.5.4