'nyquist.max_curve_magnitude': 20, # clip large values

'nyquist.max_curve_offset': 0.02, # offset of primary/mirror

'nyquist.start_marker': 'o', # marker at start of curve

'nyquist.start_marker_size': 4, # size of the maker

'nyquist.start_marker_size': 4, # size of the marker

'nyquist.circle_style': # style for unit circles

{'color': 'black', 'linestyle': 'dashed', 'linewidth': 1}

}

def nyquist_plot(

data, omega=None, plot=None, label_freq=0, color=None, label=None,

return_contour=None, title=None, legend_loc='upper right',

ax=None, **kwargs):

return_contour=None, title=None, legend_loc='upper right', ax=None,

unit_circle=False, mt_circles=None, ms_circles=None, **kwargs):

"""Nyquist plot for a system.

Generates a Nyquist plot for the system over a (optional) frequency

``omega_limits``.

color : string, optional

Used to specify the color of the line and arrowhead.

unit_circle : bool, optional

If ``True``, display the unit circle, to read gain crossover frequency.

mt_circles : array_like, optional

Draw circles corresponding to the given magnitudes of sensitivity.

ms_circles : array_like, optional

Draw circles corresponding to the given magnitudes of complementary

sensitivity.

**kwargs : :func:`matplotlib.pyplot.plot` keyword properties, optional

Additional keywords (passed to `matplotlib`)

# Mark the -1 point

plt.plot([-1], [0], 'r+')

# Label the frequencies of the points

#

# Draw circles for gain crossover and sensitivity functions

#

theta = np.linspace(0, 2*np.pi, 100)

cos = np.cos(theta)

sin = np.sin(theta)

label_pos = 15

# Display the unit circle, to read gain crossover frequency

if unit_circle:

plt.plot(cos, sin, **config.defaults['nyquist.circle_style'])

# Draw circles for given magnitudes of sensitivity

if ms_circles is not None:

for ms in ms_circles:

pos_x = -1 + (1/ms)*cos

pos_y = (1/ms)*sin

plt.plot(

pos_x, pos_y, **config.defaults['nyquist.circle_style'])

plt.text(pos_x[label_pos], pos_y[label_pos], ms)

# Draw circles for given magnitudes of complementary sensitivity

if mt_circles is not None:

for mt in mt_circles:

if mt != 1:

ct = -mt**2/(mt**2-1) # Mt center

rt = mt/(mt**2-1) # Mt radius

pos_x = ct+rt*cos

pos_y = rt*sin

plt.plot(

pos_x, pos_y,

**config.defaults['nyquist.circle_style'])

plt.text(pos_x[label_pos], pos_y[label_pos], mt)

else:

_, _, ymin, ymax = plt.axis()

pos_y = np.linspace(ymin, ymax, 100)

plt.vlines(

-0.5, ymin=ymin, ymax=ymax,

**config.defaults['nyquist.circle_style'])

plt.text(-0.5, pos_y[label_pos], 1)

# Label the frequencies of the points on the Nyquist curve

if label_freq:

ind = slice(None, None, label_freq)

omega_sys = np.imag(splane_contour[np.real(splane_contour) == 0])