如何 plot 复值 function 在 python 和 ZF02113237A5A5FFF0Z3E4 中的实变量

Question

I was trying to plot the function ((phi^n)-((-1/phi)^n))/(5^0.5) as the real part in the x-axis and imaginary part in the y-axis with matplotlib和 numpy，我用这个代码来做

#matplotlib.pyplot for the graph
import matplotlib.pyplot as plt
#numpy for mathematical operations 
from numpy import arange, real, imag, sin, cos
#phi is just a mathematical constant
phi = (1+(5**0.5))/2
#x, the domain
x = arange(0,5,0.01)
#f, the function
def f(x):
    return ((phi**(x))-((-1/phi)**(x)))/(5**0.5)
#labels for x and y axes
plt.xlabel('real')
plt.ylabel('imag')
#plot the actual graph with the label
plt.plot(real(f(x)),imag(f(x)), label='((phi**(x))-((-1/phi)**(x)))/(5**0.5)')
#show the label
plt.legend()
#show the graph
plt.show()

但是，错误RuntimeWarning: invalid value encountered in power return ((phi**(x))-((-1/phi)**(x)))/(5**0.5)在我看来

Answer 1

To plot a complex-valued function of a real variable you have to specify that the range of the function is complex numbers so that NumPy arrays are able to store complex numbers. 您可以通过将+0j添加到函数的变量来做到这一点，因此代码将是这样的

#matplotlib.pyplot for the graph
import matplotlib.pyplot as plt
#numpy for mathematical operations 
from numpy import arange, real, imag, sin, cos
#phi is just a mathematical constant
phi = (1+(5**0.5))/2
#x, the domain
x = arange(0,5,0.01)
#f, the function (notice the 'x+0j' part)
def f(x):
    return ((phi**(x+0j))-((-1/phi)**(x+0j)))/(5**0.5)
#labels for x and y axes
plt.xlabel('real')
plt.ylabel('imag')
#plot the actual graph with the label
plt.plot(real(f(x)),imag(f(x)), label='((phi**(x))-((-1/phi)**(x)))/(5**0.5)')
#show the label
plt.legend()
#show the graph
plt.show()