Question

因此，我编写了一个简单的代码，使用Matplotlib的FuncAnimation创建动画图。但是没有输出。我认为问题出在'np.append'函数中，因为如果我给'animate'函数提供预制的x，y，z数组，则代码可以正常工作。但是，我不明白为什么这行不通！

%matplotlib notebook

import numpy as np
import mpl_toolkits.mplot3d.axes3d as p3
import matplotlib.pyplot as plt
import matplotlib.animation as animation

del_t = 0.01 ##Time-step value

x=np.array([0.0])
y=np.array([10.0])
z=np.array([0.0])

#These functions give how (x, y, z) co-ordinate
#changes with time
def dx_dt(x, y, z):
    return 10*(y-x)
def dy_dt(x, y, z):
    return -x*z + 28*x - y
def dz_dt(x, y, z):
    return x*y-(8/3)*z

#Runge-Kutta Method for numerical solution of differential equations
#These functions give next (x, y, z) co-ordinate
def next_xpt(x, y, z):
    k1 = dx_dt(x, y, z) * del_t
    k2 = dx_dt(x + k1/2, y, z) * del_t
    k3 = dx_dt(x + k2/2, y, z) * del_t
    k4 = dx_dt(x + k3, y, z) * del_t
    return x + (k1 + 2*k2 + 2*k3 + k4)/6
def next_ypt(x, y, z):
    k1 = dy_dt(x, y, z) * del_t
    k2 = dy_dt(x, y + k1/2, z) * del_t
    k3 = dy_dt(x, y + k2/2, z) * del_t
    k4 = dy_dt(x, y + k3, z) * del_t
    return y + (k1 + 2*k2 + 2*k3 + k4)/6
def next_zpt(x, y, z):
    k1 = dz_dt(x, y, z) * del_t
    k2 = dz_dt(x, y, z + k1/2) * del_t
    k3 = dz_dt(x, y, z + k2/2) * del_t
    k4 = dz_dt(x, y, z + k3) * del_t
    return z + (k1 + 2*k2 + 2*k3 + k4)/6

fig = plt.figure()
ax = p3.Axes3D(fig)

#Creating a line object
line, = ax.plot3D([0.0],[10.0],[0.0],'-b') 

ax.set_xlim3d(-30,30)
ax.set_xlabel("X")
ax.set_ylim3d(-30,30)
ax.set_ylabel("Y")
ax.set_zlim3d(-30,30)
ax.set_zlabel("Z")
ax.set_title("Lorenz Strange Attractor")

def animate(i, x, y, z, line):
    np.append(x, next_xpt(x[i], y[i], z[i]))
    np.append(y, next_ypt(x[i], y[i], z[i]))
    np.append(z, next_zpt(x[i], y[i], z[i]))
    line.set_data(x[:i+1],y[:i+1])
    line.set_3d_properties(z[:i+1])
    return line

ani = animation.FuncAnimation(fig, animate, fargs = (x, y, z, line), interval=50, blit=False)

Answer 1

您需要将添加结果保存在数组x，y和z中。您看到它追加的原因是因为您很有可能正在以交互方式对其进行测试。但是正如@hpaulj提到的，出于您的目的，您将必须将附加数组存储在函数中。此外，您必须将x, y, z声明为global以反映所做的更改，以避免IndexError。要初始化线对象，可以定义一个init函数，然后在您的i中传递可迭代索引FuncAnimation

docs说（强调我的意思）

返回：append：ndarray

arr的副本，其值附加到axis。请注意，附加操作不会就地发生：已分配并填充了新数组。

您将必须存储新数组

# Initizlise x, y, z here

def init():
    line.set_data([], [])
    line.set_3d_properties([])
    return line,

# dx_dt, dy_dt, dz_dt etc. functions here 

fig = plt.figure()
ax = p3.Axes3D(fig)

#Creating a line object
line, = ax.plot3D([0.0],[10.0],[0.0],'-b') 

# Setting axes limits here    

def animate(i):
    global x, y, z
    x = np.append(x, next_xpt(x[i], y[i], z[i]))
    y = np.append(y, next_ypt(x[i], y[i], z[i]))
    z = np.append(z, next_zpt(x[i], y[i], z[i]))
    line.set_data(x[:i+1],y[:i+1])
    line.set_3d_properties(z[:i+1])
    return line,

ani = animation.FuncAnimation(fig, animate, init_func=init, interval=50, blit=False)

在Matplotlib FuncAnimation中制作动画时难以使用append函数

1 个答案: