Plot phase does not use multiple ticker when unwrapping

[mberz]

General

• pyfar version: all since addition of phase plot

Description

When plotting the unwrapped phase the MultipleFractionTicker and Formatters are not used.
I'd propose to change this and select appropriate multiples of $\pi$ also for unwrapped phase plots, as for example below.

What I Did

import pyfar as pf
import numpy as np
import matplotlib.pyplot as plt
from pyfar.plot.ticker import MultipleFractionLocator, MultipleFractionFormatter

fig, axs = plt.subplots(3, 1)
signal = pf.signals.impulse(1024, delay=4)
pf.plot.phase(signal, ax=axs[0])
pf.plot.phase(signal, ax=axs[1], unwrap=True)
pf.plot.phase(signal, ax=axs[2], unwrap=True)
axs[0].set_title('wrapped phase')
# ax[1].yaxis.set_minor_locator(MultipleFractionLocator(np.pi, 4))
axs[1].set_title('unrapped phase (default')
axs[2].yaxis.set_major_locator(MultipleFractionLocator(2, 1, np.pi))
axs[2].yaxis.set_major_formatter(MultipleFractionFormatter(2, 1, np.pi, r'\pi'))
axs[2].yaxis.set_minor_locator(MultipleFractionLocator(np.pi, 1))
axs[2].set_title('wrapped with ticks at multiples of $\pi$ (proposed)')
[ax.set_ylabel("") for ax in axs]

plt.tight_layout()