I want to plot a donut and my script is
import numpy as np
import matplotlib.pyplot as plt
pi,sin,cos = np.pi,np.sin,np.cos
r1 = 1
r2 = 2
theta = np.linspace(0,2*pi,36)
x1 = r1*cos(theta)
y1 = r1*sin(theta)
x2 = r2*cos(theta)
y2 = r2*sin(theta)
How to get a donut with red filled area ?
You can traverse the boundaries of the area in closed curve, and use fill
method to fill the area inside this closed area:
import numpy as np
import matplotlib.pyplot as plt
n, radii = 50, [.7, .95]
theta = np.linspace(0, 2*np.pi, n, endpoint=True)
xs = np.outer(radii, np.cos(theta))
ys = np.outer(radii, np.sin(theta))
# in order to have a closed area, the circles
# should be traversed in opposite directions
xs[1,:] = xs[1,::-1]
ys[1,:] = ys[1,::-1]
ax = plt.subplot(111, aspect='equal')
ax.fill(np.ravel(xs), np.ravel(ys), edgecolor='#348ABD')
plt.show()
This can easily be applied to any shape, for example, a pentagon inside or outside of a circle:
You can do this by plotting the top and bottom halves separately:
import numpy as np
import matplotlib.pyplot as plt
inner = 5.
outer = 10.
x = np.linspace(-outer, outer, 1000, endpoint=True)
yO = outer*np.sin(np.arccos(x/outer)) # x-axis values -> outer circle
yI = inner*np.sin(np.arccos(x/inner)) # x-axis values -> inner circle (with nan's beyond circle)
yI[np.isnan(yI)] = 0. # yI now looks like a boulder hat, meeting yO at the outer points
ax = plt.subplot(111)
ax.fill_between(x, yI, yO, color="red")
ax.fill_between(x, -yO, -yI, color="red")
plt.show()
Or you can use polar coordinates, though whether this is beneficial depends on the broader context:
import numpy as np
import matplotlib.pyplot as plt
theta = np.linspace(0., 2.*np.pi, 80, endpoint=True)
ax = plt.subplot(111, polar=True)
ax.fill_between(theta, 5., 10., color="red")
plt.show()
It's a bit of a hack but the following works:
import numpy as np
import matplotlib.pyplot as plt
pi,sin,cos = np.pi,np.sin,np.cos
r1 = 1
r2 = 2
theta = np.linspace(0,2*pi,36)
x1 = r1*cos(theta)
y1 = r1*sin(theta)
x2 = r2*cos(theta)
y2 = r2*sin(theta)
fig, ax = plt.subplots()
ax.fill_between(x2, -y2, y2, color='red')
ax.fill_between(x1, y1, -y1, color='white')
plt.show()
It plots the whole area of your donut in red and then plots the central "hole" in white.
The answer given by tom10 is ten ;) But if you want to define the circle (donut) origin is simple, just add the position x,y in the x, yI, yO and -yO and -yI, like this:
...
pos = [4,2]
ax.fill_between(x+pos[0], yI+pos[1], yO+pos[1], color=color)
ax.fill_between(x+pos[0], -yO+pos[1], -yI+pos[1], color=color)
...
REF Example: https://pastebin.com/8Ew4Vthb
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