当我尝试在 python 中制作 3D 图形时输入错误

Question

I know how to make 3D-graph in Python but for this one I have an error I've never seen. I want to have the graph of :

$$f(x,y)=\\frac{8\\cos(\\sqrt{x^2+y^2}}{\\sqrt{1+x^2+y^2}}$$ (LaTeX doesn't work here... ???)

My code :

    import math
    import matplotlib.pyplot as plt
    import numpy as np
    from mpl_toolkits.mplot3d import Axes3D

    ax = Axes3D(plt.figure())

    def f(x,y):
        return (8*math.cos(math.sqrt(x**2+y**2)))/(math.sqrt(1+x**2+y**2))

    X = np.arange(-1,1,0.1)
    Y = np.arange(-1,1,0.1)

    X,Y=np.meshgrid(X,Y)
    Z=f(X,Y)

    ax.plot_surface(X,Y,Z)
    plt.show()

The error :

 runfile('C:/Users/Asus/Desktop/Informatiques/nodgim.py', wdir=r'C:/Users/Asus/Desktop/Informatiques')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\Asus\Desktop\WinPython\python-3.4.3.amd64\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 680, in runfile
    execfile(filename, namespace)
  File "C:\Users\Asus\Desktop\WinPython\python-3.4.3.amd64\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 85, in execfile
    exec(compile(open(filename, 'rb').read(), filename, 'exec'), namespace)
  File "C:/Users/Asus/Desktop/Informatiques/nodgim.py", line 22, in <module>
    Z=f(X,Y)
  File "C:/Users/Asus/Desktop/Informatiques/nodgim.py", line 16, in f
    return (8*math.cos(math.sqrt(x**2+y**2)))/(math.sqrt(1+x**2+y**2))

TypeError: only length-1 arrays can be converted to Python scalars

Can you explain me what I have to do?

Thank you in advance

Answer 1

math.cos and math.sqrt expect to get a scalar value but instead were passed an array type that they cannot handle properly which results in your type error. Essentially Python's built in math functions don't know how to deal with numpy arrays, so to fix this you need to use the mathematical functions that numpy provides to work on these data types: numpy.cos and numpy.sqrt

This will then give you the vectorization you need.