Pyfar

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* Make python-soundfile an optional requirement due to unsupported architectures. Note that without python-soundfile common audio file format are no longer supported via `pyfar.io` (PR 334, 340).
* Developer: Switch to CircleCI for continuous testing (PR 336).

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* Bugfix: Sweep functions marked for deprecation had no return value.

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* Bugfix: do not allow 'flat' shading parameter in 2D plot functions (PR 291)

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* `pyfar.plot`

* The plot module was largely extended by 2D color coded versions of the former line plot functions: `time_2d`, `freq_2d`, `phase_2d`, `group_delay_2d`, `time_freq_2d`, `freq_phase_2d` and `freq_group_delay_2d`. New shortcuts for interactive plots were added to cycle between line and 2D plots and to toggle between vertical and horizontal orientation of 2D plots. (PR 198, 273, 276)
* The `xscale` parameter was replaced by the more explicit `freq_scale` parameter in all plot functions. It will be removed in pyfar 0.6.0 (PR 282)

* `pyfar.filter`

* Added cascaded shelving filters `low_shelve_cascade` and `high_shelve_cascade` used to generate filters with a user definable slope given in dB per octaves within a certain frequency region. (PR 284)

* `pyfar.Signal`

* Added a `freq_raw` property, which is the frequency spectrum without normalization. It enables easy access and reduces complexity in internal computations. (PR 274)

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* More reasonable handling of FFT normalizations in `arithmetic operations <https://pyfar.readthedocs.io/en/latest/concepts/pyfar.arithmetic_operations.html>`_. This is a major change and might break backwards compatibility in some cases (although this is unlikely to happen, PR #253, 245, 235).
* The documentation now contains `concepts <https://pyfar.readthedocs.io/en/latest/concepts.html>`_ behind pyfar in a separate section. This makes the concepts easier to find and understand and the documentation of the classes and functions cleaner (PR #251, 243).

* `pyfar.dsp`

* Added `convolve` for convolution of signals in the time and frequency domain (PR 232)
* Added `deconvolve` for frequency domain deconvolution with the optional regularization (PR 212)
* functions in the `filter` module have more verbose names, e.g., 'butterworth' instead of 'butter'. Functions with old names will be deprecated in pyfar 0.5.0 (PR 248).
* `time_window` can now return the window to make it easier to inspect windows and apply windows multiple times (PR 247)
* the dB parameters in `spectrogram` obsolete. They were thus removed and can be controlled in the plot function `pyfar.plot.spectrogram` instead (PR 258, 256).

* `pyfar.io`

* `pyfar.io.read` and `pyfar.io.write` can now handle Python built in data types (PR 205)
* added `read_audio` and `write_audio` to support more types of audio files (based on the `soundfile` package). The old functions `read_wav` and `write_wav` will be deprecated in pyfar 0.5.0 (PR 234)
* `read_sofa` can now also load SOFA files of DataType 'TransferFunction' (e.g. GeneralTF) and uses the `sofar <https://sofar.readthedocs.io>`_ package (PR #254, 240).

* `pyfar.plot`

* Plots of the magnitude spectrum now use ``10`` as the new default `log_prefix` for calculating the level in dB for plotting Signals with the FFT normalizations ``'psd'`` and ``'power'`` (PR 260)
* Improved handling of colorbar in `pyfar.plot.spectrogram`. A speparate axis for the colorbar can be passed to the function. The function can return the axis of the colorbar. (PR 216)
* `custom_subplot` now returns axis handles (PR 237)
* Frequency plots allow to show negative frequencies (PR 233)

* Filter classes (`pyfar.FilterFIR`, `pyfar.FilterIIR`, `pyfar.FilterSOS`)

* Rename the property `shape` to `n_channels`. pyfar Filter objects do not support multi-dimensional layouts (PR 102)
* Filter states can now be saved to allow block-wise processing (PR 102)
* The `coefficients` can now be set. This allows to mimic time variant systems in block-wise processing (PR 252)
* Improved documentation (PR 252)

* Audio classes (`pyfar.Signal`, `pyfar.TimeData`, `pyfar.FrequencyData`)

* Make arithmetic operations available as `pyfar.add`, `pyfar.subtract`, etc. (PR 230)
* Remove fft normalizations from FrequencyData (PR 225)

* `pyfar.Coordinates` and `pyfar.Orientations`

* Renamed methods `pyfar.Coordinates.get_nearest_*` to `pyfar.Coordinates.find_nearest_*`. Old methods will be deprecated in pyfar 0.5.0 (PR 209)
* The plots generated by `Coordinates.show` and `Orientations.show` now use the pyfar plot style (PR 169)

* `pyfar.signals`

* renamed `pyfar.signals.linear_sweep` to `pyfar.signals.linear_sweep_time` and `pyfar.signals.exponential_sweep` to `pyfar.signals.exponential_sweep_time`. Old functions will be deprecated in pyfar 0.5.0 (PR 201)

* CI: Only test wheels to save time during testing (PR 236)
* Enhanced contributing guidelines (PR 239)

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* Fix broken install on Python 3.9