Here is a small modification of Kyler Brown's solution for Python that also allows negative values on the polar axes (which are currently not officially supported by matplotlib), basically by simply removing the check for negative values from set_rgrids:
import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns # improves plot aesthetics
def _invert(x, limits):
"""inverts a value x on a scale from
limits[0] to limits[1]"""
return limits[1] - (x - limits[0])
def _scale_data(data, ranges):
"""scales data[1:] to ranges[0],
inverts if the scale is reversed"""
# for d, (y1, y2) in zip(data[1:], ranges[1:]):
for d, (y1, y2) in zip(data, ranges):
assert (y1 <= d <= y2) or (y2 <= d <= y1)
x1, x2 = ranges[0]
d = data[0]
if x1 > x2:
d = _invert(d, (x1, x2))
x1, x2 = x2, x1
sdata = [d]
for d, (y1, y2) in zip(data[1:], ranges[1:]):
if y1 > y2:
d = _invert(d, (y1, y2))
y1, y2 = y2, y1
sdata.append((d-y1) / (y2-y1) * (x2 - x1) + x1)
return sdata
def set_rgrids(self, radii, labels=None, angle=None, fmt=None,
**kwargs):
"""
Set the radial locations and labels of the *r* grids.
The labels will appear at radial distances *radii* at the
given *angle* in degrees.
*labels*, if not None, is a ``len(radii)`` list of strings of the
labels to use at each radius.
If *labels* is None, the built-in formatter will be used.
Return value is a list of tuples (*line*, *label*), where
*line* is :class:`~matplotlib.lines.Line2D` instances and the
*label* is :class:`~matplotlib.text.Text` instances.
kwargs are optional text properties for the labels:
%(Text)s
ACCEPTS: sequence of floats
"""
# Make sure we take into account unitized data
radii = self.convert_xunits(radii)
radii = np.asarray(radii)
rmin = radii.min()
# if rmin <= 0:
# raise ValueError('radial grids must be strictly positive')
self.set_yticks(radii)
if labels is not None:
self.set_yticklabels(labels)
elif fmt is not None:
self.yaxis.set_major_formatter(FormatStrFormatter(fmt))
if angle is None:
angle = self.get_rlabel_position()
self.set_rlabel_position(angle)
for t in self.yaxis.get_ticklabels():
t.update(kwargs)
return self.yaxis.get_gridlines(), self.yaxis.get_ticklabels()
class ComplexRadar():
def __init__(self, fig, variables, ranges,
n_ordinate_levels=6):
angles = np.arange(0, 360, 360./len(variables))
axes = [fig.add_axes([0.1,0.1,0.9,0.9],polar=True,
label = "axes{}".format(i))
for i in range(len(variables))]
l, text = axes[0].set_thetagrids(angles,
labels=variables)
[txt.set_rotation(angle-90) for txt, angle
in zip(text, angles)]
for ax in axes[1:]:
ax.patch.set_visible(False)
ax.grid("off")
ax.xaxis.set_visible(False)
for i, ax in enumerate(axes):
grid = np.linspace(*ranges[i],
num=n_ordinate_levels)
gridlabel = ["{}".format(round(x,2))
for x in grid]
if ranges[i][0] > ranges[i][1]:
grid = grid[::-1] # hack to invert grid
# gridlabels aren't reversed
gridlabel[0] = "" # clean up origin
# ax.set_rgrids(grid, labels=gridlabel, angle=angles[i])
set_rgrids(ax, grid, labels=gridlabel, angle=angles[i])
#ax.spines["polar"].set_visible(False)
ax.set_ylim(*ranges[i])
# variables for plotting
self.angle = np.deg2rad(np.r_[angles, angles[0]])
self.ranges = ranges
self.ax = axes[0]
def plot(self, data, *args, **kw):
sdata = _scale_data(data, self.ranges)
self.ax.plot(self.angle, np.r_[sdata, sdata[0]], *args, **kw)
def fill(self, data, *args, **kw):
sdata = _scale_data(data, self.ranges)
self.ax.fill(self.angle, np.r_[sdata, sdata[0]], *args, **kw)
# example data
variables = ("Normal Scale", "Inverted Scale", "Inverted 2",
"Normal Scale 2", "Normal 3", "Normal 4 %", "Inverted 3 %")
data = (-1.76, 1.1, 1.2,
4.4, 3.4, 86.8, 20)
ranges = [(-5, 3), (1.5, 0.3), (1.3, 0.5),
(1.7, 4.5), (1.5, 3.7), (70, 87), (100, -50)]
# plotting
fig1 = plt.figure(figsize=(6, 6))
radar = ComplexRadar(fig1, variables, ranges)
radar.plot(data)
radar.fill(data, alpha=0.2)
plt.show()
