如何为多个点设置动画以围绕单个点独立旋转？

Question

我正在尝试构建一个散点图并且对动画感到困惑。 最终，我希望有 >1000 个点，以 (0,0) 附近的随机正态分布绘制。 然后每个点应以不同的速度围绕 (0,0) 顺时针或逆时针旋转。

我试图用一个循环 function 来做到这一点，它会随机移动，但它非常慢，而且到目前为止我还无法进行超过一个点的移动：

import numpy as np
import matplotlib.pyplot as plt
plt.rcParams["figure.figsize"] = 4,3
from matplotlib.animation import FuncAnimation
from math import sqrt, exp
from matplotlib.animation import FuncAnimation, PillowWriter

fig, ax = plt.subplots()
# set the axes limits
ax.axis([-2.5,2.5,-2.5,2.5])
# set equal aspect such that the circle is not shown as ellipse
ax.set_aspect("equal")
# create a point in the axes

for i in range(0,6):
    x = np.random.normal()
    y = np.random.normal()
    r = np.sqrt(x*x+y*y)
    def circle(phi):
        return np.array([r*np.cos(phi), r*np.sin(phi)])
    point, = ax.plot(x,y, marker="o")
    ani = FuncAnimation(fig, update, interval=10, blit=True, repeat=True,
                    frames=np.linspace(0,2*np.pi,360, endpoint=False))
    
plt.show()

writer = PillowWriter(fps=25) 
ani.save(r'[path --> .gif]', writer=writer)

如何修复此代码？

Answer 1

这是你想要的吗？

import numpy as np
import matplotlib.pyplot as plt
plt.rcParams["figure.figsize"] = 4,3
from matplotlib.animation import FuncAnimation
from math import sqrt, exp


fig, ax = plt.subplots()
# set the axes limits
ax.axis([-2.5,2.5,-2.5,2.5])
# set equal aspect such that the circle is not shown as ellipse
ax.set_aspect("equal")
# create a point in the axes

def update(i):
    x = np.random.normal()
    y = np.random.normal()
    r = np.sqrt(x*x+y*y)
    def circle(phi):
        return np.array([r*np.cos(phi), r*np.sin(phi)])
    ax.plot(x,y, marker="o")

ani = FuncAnimation(fig, func=update, interval=10, blit=False, repeat=True,
                frames=np.linspace(0,2*np.pi,360, endpoint=False))

plt.show()

Answer 2

我不太清楚如何更新您的代码以获得解决方案。 但我想出了这个，它使用了一些相同的逻辑：

import matplotlib as mpl
from matplotlib.animation import FuncAnimation
import matplotlib.pyplot as plt
import numpy as np

# how many points to draw
points = 100

# generating x & y coordinates, their distance from origin,
# their angle relative to the origin, and random rotations to
# apply to each point each frame
xs = np.random.uniform(-1, 1, points)
ys = np.random.uniform(-1, 1, points)
ls = np.sqrt(xs**2 + ys**2)
angles = np.arctan2(ys, xs)
negs = np.random.choice([-1, 1], size=points)
rotations = (np.random.uniform(np.pi/50, np.pi/6, size=points) * negs)

# initialize a figure, make a color range to color each point
fig, ax = plt.subplots(figsize=(4,4))
ax.set_xlim(-1.5,1.5)
ax.set_ylim(-1.5,1.5)
color_divisions = [(1/points)*i for i in range(points)]
cmap = mpl.cm.get_cmap('jet')
colors = cmap(color_divisions)

# update function
# update gets fed elements from the frames parameter of FuncAnimation
# each update we clear the graph (but reapply the same x/y limits)
# we then draw the points as a scatter and update the data for the next frame
# add each rotation to each angle, and then calculate the new x and y coordinates
# with numpy these calculations can be done w/o a loop, but global is needed
# to update variables from the global scope
def update(f):
    global xs, ys, angles, rotations
    ax.clear()
    ax.set_xlim(-1.5,1.5)
    ax.set_ylim(-1.5,1.5)
    ax.scatter(xs, ys, color=colors)
    angles += rotations
    ys = np.sin(angles) * ls
    xs = np.cos(angles) * ls

#call the animation and save
ani = FuncAnimation(fig, update, interval=200, frames=range(100))
ani.save('ani.gif', writer='pillow')

产生以下 animation 以随机速度绕原点旋转 100 个点：

您可以增加点数（对于 1000 个点，这可能会变得非常慢），调整 FPS（ interval ）或每个点的旋转量。