Matplotlib draws three-dimensional scatter and surface graphs

This blog post mainly introduces how to use matplotlib The library draws three-dimensional scatter diagrams and surface diagrams .

Three dimensional scatter plot

numpy Of random.rand(d0,d1,d2…) Function generates obedience according to dimension 0~1 Uniformly distributed random sample points ;
x、y、z They are all one-dimensional arrays

# -*- coding: utf-8 -*-

import matplotlib.pyplot as plt
import numpy as np

def randrange(n, vmin, vmax):
    return (vmax - vmin)*np.random.rand(n) 

fig = plt.figure()
ax = fig.add_subplot(projection="3d")

n = 100
x = randrange(n,0,20)
y = randrange(n,0,20)
z = randrange(n,-30,-5)

ax.scatter(x,y,z,marker="^")
ax.set_xlabel("X Label")
ax.set_ylabel("Y Label")
ax.set_zlabel("Z Label")

ax.set_title("3D scatter plot")
plt.show()

3D Surface graph

Here we need to use numpy Of meshgrid() Function generation x and y Grid point coordinates (x,y), That is to say, put the first and second coordinates of the elements in the Cartesian product of two arrays into two matrices respectively . When drawing a surface ,z It has to be two-dimensional .

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(projection="3d")

x = np.arange(-5,5,0.5)
y = np.arange(-5,5,0.5)
x,y = np.meshgrid(x, y)
z = np.sqrt(x**2 + y**2)

ax.plot_surface(x,y,z)
ax.set_xlabel("X Label")
ax.set_ylabel("Y Label")
ax.set_zlabel("Z Label")

ax.set_title("3D surface plot")
plt.show()

When drawing a surface , We can also add color and colorbar

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(projection="3d")

x = np.arange(-5,5,0.5)
y = np.arange(-5,5,0.5)
x,y = np.meshgrid(x, y)
z = np.sqrt(x**2 + y**2)

#rstride Indicates the line step size ,cmap Color the surface 
surf = ax.plot_surface(x,y,z,rstride=1,cstride=1,cmap=plt.cm.viridis)
#colorbar You can add a color bar to the image 
fig.colorbar(surf)
ax.set_xlabel("X Label")
ax.set_ylabel("Y Label")
ax.set_zlabel("Z Label")

ax.set_title("3D surface plot")
plt.show()