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Commitae8d586

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Merge pull request#723 from roryyorke/rory/nichols-improvements
Improvements to Nichols chart plotting
2 parentsdd95f35 +59cd872 commitae8d586

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2 files changed

+159
-27
lines changed

2 files changed

+159
-27
lines changed

‎control/nichols.py

Lines changed: 91 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -51,6 +51,8 @@
5151

5252
importnumpyasnp
5353
importmatplotlib.pyplotasplt
54+
importmatplotlib.transforms
55+
5456
from .ctrlutilimportunwrap
5557
from .freqplotimport_default_frequency_range
5658
from .importconfig
@@ -119,7 +121,18 @@ def nichols_plot(sys_list, omega=None, grid=None):
119121
nichols_grid()
120122

121123

122-
defnichols_grid(cl_mags=None,cl_phases=None,line_style='dotted'):
124+
def_inner_extents(ax):
125+
# intersection of data and view extents
126+
# if intersection empty, return view extents
127+
_inner=matplotlib.transforms.Bbox.intersection(ax.viewLim,ax.dataLim)
128+
if_innerisNone:
129+
returnax.ViewLim.extents
130+
else:
131+
return_inner.extents
132+
133+
134+
defnichols_grid(cl_mags=None,cl_phases=None,line_style='dotted',ax=None,
135+
label_cl_phases=True):
123136
"""Nichols chart grid
124137
125138
Plots a Nichols chart grid on the current axis, or creates a new chart
@@ -136,17 +149,36 @@ def nichols_grid(cl_mags=None, cl_phases=None, line_style='dotted'):
136149
line_style : string, optional
137150
:doc:`Matplotlib linestyle\
138151
<matplotlib:gallery/lines_bars_and_markers/linestyles>`
152+
ax : matplotlib.axes.Axes, optional
153+
Axes to add grid to. If ``None``, use ``plt.gca()``.
154+
label_cl_phases: bool, optional
155+
If True, closed-loop phase lines will be labelled.
139156
157+
Returns
158+
-------
159+
cl_mag_lines: list of `matplotlib.line.Line2D`
160+
The constant closed-loop gain contours
161+
cl_phase_lines: list of `matplotlib.line.Line2D`
162+
The constant closed-loop phase contours
163+
cl_mag_labels: list of `matplotlib.text.Text`
164+
mcontour labels; each entry corresponds to the respective entry
165+
in ``cl_mag_lines``
166+
cl_phase_labels: list of `matplotlib.text.Text`
167+
ncontour labels; each entry corresponds to the respective entry
168+
in ``cl_phase_lines``
140169
"""
170+
ifaxisNone:
171+
ax=plt.gca()
172+
141173
# Default chart size
142174
ol_phase_min=-359.99
143175
ol_phase_max=0.0
144176
ol_mag_min=-40.0
145177
ol_mag_max=default_ol_mag_max=50.0
146178

147-
# Find bounds of the current dataset,ifthere is one.
148-
ifplt.gcf().gca().has_data():
149-
ol_phase_min,ol_phase_max,ol_mag_min,ol_mag_max=plt.axis()
179+
ifax.has_data():
180+
# Find extent of intersection the current dataset or view
181+
ol_phase_min,ol_mag_min,ol_phase_max,ol_mag_max=_inner_extents(ax)
150182

151183
# M-circle magnitudes.
152184
ifcl_magsisNone:
@@ -165,19 +197,22 @@ def nichols_grid(cl_mags=None, cl_phases=None, line_style='dotted'):
165197
ol_mag_min+cl_mag_step,cl_mag_step)
166198
cl_mags=np.concatenate((extended_cl_mags,key_cl_mags))
167199

200+
# a minimum 360deg extent containing the phases
201+
phase_round_max=360.0*np.ceil(ol_phase_max/360.0)
202+
phase_round_min=min(phase_round_max-360,
203+
360.0*np.floor(ol_phase_min/360.0))
204+
168205
# N-circle phases (should be in the range -360 to 0)
169206
ifcl_phasesisNone:
170-
# Choose a reasonable set of default phases (denser if the open-loop
171-
# data is restricted to a relatively small range of phases).
172-
key_cl_phases=np.array([-0.25,-45.0,-90.0,-180.0,-270.0,
173-
-325.0,-359.75])
174-
ifnp.abs(ol_phase_max-ol_phase_min)<90.0:
175-
other_cl_phases=np.arange(-10.0,-360.0,-10.0)
176-
else:
177-
other_cl_phases=np.arange(-10.0,-360.0,-20.0)
178-
cl_phases=np.concatenate((key_cl_phases,other_cl_phases))
179-
else:
180-
assert ((-360.0<np.min(cl_phases))and (np.max(cl_phases)<0.0))
207+
# aim for 9 lines, but always show (-360+eps, -180, -eps)
208+
# smallest spacing is 45, biggest is 180
209+
phase_span=phase_round_max-phase_round_min
210+
spacing=np.clip(round(phase_span/8/45)*45,45,180)
211+
key_cl_phases=np.array([-0.25,-359.75])
212+
other_cl_phases=np.arange(-spacing,-360.0,-spacing)
213+
cl_phases=np.unique(np.concatenate((key_cl_phases,other_cl_phases)))
214+
elifnot ((-360<np.min(cl_phases))and (np.max(cl_phases)<0.0)):
215+
raiseValueError('cl_phases must between -360 and 0, exclusive')
181216

182217
# Find the M-contours
183218
m=m_circles(cl_mags,phase_min=np.min(cl_phases),
@@ -196,27 +231,57 @@ def nichols_grid(cl_mags=None, cl_phases=None, line_style='dotted'):
196231
# over the range -360 < phase < 0. Given the range
197232
# the base chart is computed over, the phase offset should be 0
198233
# for -360 < ol_phase_min < 0.
199-
phase_offset_min=360.0*np.ceil(ol_phase_min/360.0)
200-
phase_offset_max=360.0*np.ceil(ol_phase_max/360.0)+360.0
201-
phase_offsets=np.arange(phase_offset_min,phase_offset_max,360.0)
234+
phase_offsets=360+np.arange(phase_round_min,phase_round_max,360.0)
235+
236+
cl_mag_lines= []
237+
cl_phase_lines= []
238+
cl_mag_labels= []
239+
cl_phase_labels= []
202240

203241
forphase_offsetinphase_offsets:
204242
# Draw M and N contours
205-
plt.plot(m_phase+phase_offset,m_mag,color='lightgray',
206-
linestyle=line_style,zorder=0)
207-
plt.plot(n_phase+phase_offset,n_mag,color='lightgray',
208-
linestyle=line_style,zorder=0)
243+
cl_mag_lines.extend(
244+
ax.plot(m_phase+phase_offset,m_mag,color='lightgray',
245+
linestyle=line_style,zorder=0))
246+
cl_phase_lines.extend(
247+
ax.plot(n_phase+phase_offset,n_mag,color='lightgray',
248+
linestyle=line_style,zorder=0))
209249

210250
# Add magnitude labels
211251
forx,y,minzip(m_phase[:][-1]+phase_offset,m_mag[:][-1],
212252
cl_mags):
213253
align='right'ifm<0.0else'left'
214-
plt.text(x,y,str(m)+' dB',size='small',ha=align,
215-
color='gray')
254+
cl_mag_labels.append(
255+
ax.text(x,y,str(m)+' dB',size='small',ha=align,
256+
color='gray',clip_on=True))
257+
258+
# phase labels
259+
iflabel_cl_phases:
260+
forx,y,pinzip(n_phase[:][0]+phase_offset,
261+
n_mag[:][0],
262+
cl_phases):
263+
ifp>-175:
264+
align='right'
265+
elifp>-185:
266+
align='center'
267+
else:
268+
align='left'
269+
cl_phase_labels.append(
270+
ax.text(x,y,f'{round(p)}\N{DEGREE SIGN}',
271+
size='small',
272+
ha=align,
273+
va='bottom',
274+
color='gray',
275+
clip_on=True))
276+
216277

217278
# Fit axes to generated chart
218-
plt.axis([phase_offset_min-360.0,phase_offset_max-360.0,
219-
np.min(cl_mags),np.max([ol_mag_max,default_ol_mag_max])])
279+
ax.axis([phase_round_min,
280+
phase_round_max,
281+
np.min(np.concatenate([cl_mags,[ol_mag_min]])),
282+
np.max([ol_mag_max,default_ol_mag_max])])
283+
284+
returncl_mag_lines,cl_phase_lines,cl_mag_labels,cl_phase_labels
220285

221286
#
222287
# Utility functions

‎control/tests/nichols_test.py

Lines changed: 68 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,9 +3,11 @@
33
RMM, 31 Mar 2011
44
"""
55

6+
importmatplotlib.pyplotasplt
7+
68
importpytest
79

8-
fromcontrolimportStateSpace,nichols_plot,nichols
10+
fromcontrolimportStateSpace,nichols_plot,nichols,nichols_grid,pade,tf
911

1012

1113
@pytest.fixture()
@@ -26,3 +28,68 @@ def test_nichols(tsys, mplcleanup):
2628
deftest_nichols_alias(tsys,mplcleanup):
2729
"""Test the control.nichols alias and the grid=False parameter"""
2830
nichols(tsys,grid=False)
31+
32+
33+
@pytest.mark.usefixtures("mplcleanup")
34+
classTestNicholsGrid:
35+
deftest_ax(self):
36+
# check grid is plotted into gca, or specified axis
37+
fig,axs=plt.subplots(2,2)
38+
plt.sca(axs[0,1])
39+
40+
cl_mag_lines=nichols_grid()[1]
41+
assertcl_mag_lines[0].axesisaxs[0,1]
42+
43+
cl_mag_lines=nichols_grid(ax=axs[1,1])[1]
44+
assertcl_mag_lines[0].axesisaxs[1,1]
45+
# nichols_grid didn't change what the "current axes" are
46+
assertplt.gca()isaxs[0,1]
47+
48+
49+
deftest_cl_phase_label_control(self):
50+
# test label_cl_phases argument
51+
cl_mag_lines,cl_phase_lines,cl_mag_labels,cl_phase_labels \
52+
=nichols_grid()
53+
assertlen(cl_phase_labels)>0
54+
55+
cl_mag_lines,cl_phase_lines,cl_mag_labels,cl_phase_labels \
56+
=nichols_grid(label_cl_phases=False)
57+
assertlen(cl_phase_labels)==0
58+
59+
60+
deftest_labels_clipped(self):
61+
# regression test: check that contour labels are clipped
62+
mcontours,ncontours,mlabels,nlabels=nichols_grid()
63+
assertall(ml.get_clip_on()formlinmlabels)
64+
assertall(nl.get_clip_on()fornlinnlabels)
65+
66+
67+
deftest_minimal_phase(self):
68+
# regression test: phase extent is minimal
69+
g=tf([1],[1,1])*tf([1],[1/1,2*0.1/1,1])
70+
nichols(g)
71+
ax=plt.gca()
72+
assertax.get_xlim()[1]<=0
73+
74+
75+
deftest_fixed_view(self):
76+
# respect xlim, ylim set by user
77+
g= (tf([1],[1/1,2*0.01/1,1])
78+
*tf([1],[1/100**2,2*0.001/100,1])
79+
*tf(*pade(0.01,5)))
80+
81+
# normally a broad axis
82+
nichols(g)
83+
84+
assert(plt.xlim()[0]==-1440)
85+
assert(plt.ylim()[0]<=-240)
86+
87+
nichols(g,grid=False)
88+
89+
# zoom in
90+
plt.axis([-360,0,-40,50])
91+
92+
# nichols_grid doesn't expand limits
93+
nichols_grid()
94+
assert(plt.xlim()[0]==-360)
95+
assert(plt.ylim()[1]>=-40)

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