如何制作顺时针图?有人问了类似的问题here:How to make the angles in a matplotlib polar plot go clockwise with 0° at the top?
但我不明白这一点。
import matplotlib.pyplot as plt
import numpy as np
fig = plt.figure()
ax = fig.add_subplot(111, polar=True)
ax.grid(True)
theta = np.arange(0,370,10)
theta = [i*np.pi/180.0 for i in theta] # convert to radians
x = [3.00001,3,3,3,3,3,3,3,3,3,3,3,3,3,2.5,2,2,2,2,2,1.5,1.5,1,1.5,2,2,2.5,2.5,3,3,3,3,3,3,3,3,3]
ax.plot(theta, x)
plt.show()
编辑:
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.projections import PolarAxes, register_projection
from matplotlib.transforms import Affine2D, Bbox, IdentityTransform
class NorthPolarAxes(PolarAxes):
'''
A variant of PolarAxes where theta starts pointing north and goes
clockwise.
'''
name = 'northpolar'
class NorthPolarTransform(PolarAxes.PolarTransform):
def transform(self, tr):
xy = np.zeros(tr.shape, np.float_)
t = tr[:, 0:1]
r = tr[:, 1:2]
x = xy[:, 0:1]
y = xy[:, 1:2]
x[:] = r * np.sin(t)
y[:] = r * np.cos(t)
return xy
transform_non_affine = transform
def inverted(self):
return NorthPolarAxes.InvertedNorthPolarTransform()
class InvertedNorthPolarTransform(PolarAxes.InvertedPolarTransform):
def transform(self, xy):
x = xy[:, 0:1]
y = xy[:, 1:]
r = np.sqrt(x*x + y*y)
fig = plt.figure()
register_projection(NorthPolarAxes)
ax=plt.subplot(1, 1, 1, projection='northpolar')
theta=np.linspace(0,2*np.pi,37)
x = [3.00001,3,3,3,3,3,3,3,3,3,3,3,3,3,2.5,2,2,2,2,
2,1.5,1.5,1,1.5,2,2,2.5,2.5,3,3,3,3,3,3,3,3,3]
ax.plot(theta, x)
plt.show()
如何正确使用register_projection(NorthPolarAxes)?
答案 0 :(得分:16)
添加这些字符串:
ax.set_theta_direction(-1)
ax.set_theta_offset(pi/2.0)
答案 1 :(得分:7)
ax.set_theta_direction(-1)
ax.set_theta_direction('N')
稍微易于理解。
答案 2 :(得分:3)
修改:请注意,Pavel提供了much better solution!
您链接的SO问题包含答案。以下是ptomato's NorthPolarAxes
class的略微修改版本,theta=0
指向东方并顺时针增加:
import matplotlib.pyplot as plt
import numpy as np
import matplotlib.projections as projections
import matplotlib.transforms as mtransforms
class EastPolarAxes(projections.PolarAxes):
'''
A variant of PolarAxes where theta starts pointing East and goes
clockwise.
https://stackoverflow.com/questions/2417794/2433287#2433287
https://stackoverflow.com/questions/7664153/7664545#7664545
'''
name = 'eastpolar'
class EastPolarTransform(projections.PolarAxes.PolarTransform):
"""
The base polar transform. This handles projection *theta* and
*r* into Cartesian coordinate space *x* and *y*, but does not
perform the ultimate affine transformation into the correct
position.
"""
def transform(self, tr):
xy = np.zeros(tr.shape, np.float_)
t = tr[:, 0:1]
r = tr[:, 1:2]
x = xy[:, 0:1]
y = xy[:, 1:2]
x[:] = r * np.cos(-t)
y[:] = r * np.sin(-t)
return xy
transform_non_affine = transform
def inverted(self):
return EastPolarAxes.InvertedEastPolarTransform()
class InvertedEastPolarTransform(projections.PolarAxes.InvertedPolarTransform):
"""
The inverse of the polar transform, mapping Cartesian
coordinate space *x* and *y* back to *theta* and *r*.
"""
def transform(self, xy):
x = xy[:, 0:1]
y = xy[:, 1:]
r = np.sqrt(x*x + y*y)
theta = npy.arccos(x / r)
theta = npy.where(y > 0, 2 * npy.pi - theta, theta)
return np.concatenate((theta, r), 1)
def inverted(self):
return EastPolarAxes.EastPolarTransform()
def _set_lim_and_transforms(self):
projections.PolarAxes._set_lim_and_transforms(self)
self.transProjection = self.EastPolarTransform()
self.transData = (
self.transScale +
self.transProjection +
(self.transProjectionAffine + self.transAxes))
self._xaxis_transform = (
self.transProjection +
self.PolarAffine(mtransforms.IdentityTransform(), mtransforms.Bbox.unit()) +
self.transAxes)
self._xaxis_text1_transform = (
self._theta_label1_position +
self._xaxis_transform)
self._yaxis_transform = (
mtransforms.Affine2D().scale(np.pi * 2.0, 1.0) +
self.transData)
self._yaxis_text1_transform = (
self._r_label1_position +
mtransforms.Affine2D().scale(1.0 / 360.0, 1.0) +
self._yaxis_transform)
def eastpolar_axes():
projections.register_projection(EastPolarAxes)
ax=plt.subplot(1, 1, 1, projection='eastpolar')
theta=np.linspace(0,2*np.pi,37)
x = [3.00001,3,3,3,3,3,3,3,3,3,3,3,3,3,2.5,2,2,2,2,
2,1.5,1.5,1,1.5,2,2,2.5,2.5,3,3,3,3,3,3,3,3,3]
ax.plot(theta, x)
plt.show()
eastpolar_axes()
来自matplotlib/projections/polar.py
的{{1}}和PolarTransform
的文档字符串已添加,因为我认为它们有助于解释每个组件的功能。这将指导您更改公式。
要获得顺时针行为,只需更改InvertedPolarTransform
- > t
:
-t
并且在 x[:] = r * np.cos(-t)
y[:] = r * np.sin(-t)
中,我们希望在InvertedEastPolarTransform
(上半部分)而不是2 * npy.pi - theta
时使用y > 0
。