Detailed explanation of drawing three-dimensional graphs in Python

Use Python to draw 3D graphs

Goal: draw image $z^2=x^2+y^2$

import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.mplot3d import Axes3D #绘制3D图案

The first step in drawing a surface is to create a two-dimensional grid. In Python, we use meshgrid()functions, and this function is also used in matlab.

Create data: first create x and y, their range is (-1,1)

x = np.linspace(-1,1,100)
y = np.linspace(-1,1,50)

Then call the meshgrid function in numpy to perform meshing operations.

x_,y_ = np.meshgrid(x,y,indexing='ij') 

x_, y_ returns a grid array. By printing the shapes of x_ and y_, you can see that x_, y_ are two-dimensional arrays of (100*50), that is, the length of the array x is multiplied by the length of the array y

print(x_.shape,y_.shape)  

(100, 50) (100, 50)

Gridding unifies the dimensions of X and Y. When performing array operations, more data is involved and the scope is wider.

z_ = x_**2 + y_**2

draw graphics

plt.figure(): custom image.add_subplot
(): add subgraph.plot_surface
(): draw surface.colorbar
(): add color bar

fig = plt.figure(figsize=(12,8),facecolor='white') #创建图片
sub = fig.add_subplot(111,projection='3d')# 添加子图，
surf = sub.plot_surface(x_,y_,z_,cmap=plt.cm.brg) #绘制曲面,并设置颜色cmap
cb = fig.colorbar(surf,shrink=0.8,aspect=15) #设置颜色棒


sub.set_xlabel(r"$x$")
sub.set_ylabel(r"$y$")
sub.set_zlabel(r"$z$")
plt.show()

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full code

import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.mplot3d import Axes3D #绘制3D图案

x = np.linspace(-1,1,100)
y = np.linspace(-1,1,50)
x_,y_ = np.meshgrid(x,y,indexing='ij') 
z_ = x_**2 + y_**2
fig = plt.figure(figsize=(12,8),facecolor='white') #创建图片
sub = fig.add_subplot(111,projection='3d')# 添加子图，
surf = sub.plot_surface(x_,y_,z_,cmap=plt.cm.brg) #绘制曲面,并设置颜色cmap
cb = fig.colorbar(surf,shrink=0.8,aspect=15) #设置颜色棒

sub.set_xlabel(r"$x$")
sub.set_ylabel(r"$y$")
sub.set_zlabel(r"$z$")
plt.show()