问题
I am new to Python plotting apart from some basic knowledge of matplotlib.pyplot. My question is how to plot some higher degree polynomials? One method I saw was expressing y in terms of x and then plotting the values. But I have 2 difficulties:
- y and x cannot be separated.
- I am expecting a closed curve(actually a complicated curve)
The polynomial I am trying to plot is:
c0 + c1*x + c2*y +c3*x*x + c4*x*y + c5*y*y + c6*x**3 + c7*x**2*y + ..... c26*x*y**5 + c27*y**6
All coefficients c0 to c27 are known.
How do I plot this curve?
Also could you please suggest me resources from where I can learn plotting and visualization in Python?
Clarification: Sorry everyone for not making it clear enough. It is not an equation of a surface (which involves 3 variables: x, y and z). I should have put a zero at the end: c0 + c1*x + c2*y +c3*x*x + c4*x*y + c5*y*y + c6*x**3 + c7*x**2*y + ..... c26*x*y**5 + c27*y**6 =0
回答1:
I'm not sure I fully understood your question, but I think you want a surface plot
import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
x = np.arange(-5, 5, 0.25)
y = np.arange(-5, 5, 0.25)
X, Y = np.meshgrid(x, y)
F = 3 + 2*X + 4*X*Y + 5*X*X
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.plot_surface(X, Y, F)
plt.show()
And for the resources: official documentation and pyvideos
回答2:
Your equation represents a 3D surface, which you can plot creating first a mesh grid of x and y values, easily achieved using numpy:
X,Y = np.meshgrid( np.linspace( xmin, xmax, 100), np.linspace( ymin, ymax, 200) )
X and Y are both 2D arrays containing the X and Y coordinates, respectively.
Then you can calculate z values for each point in this mesh, using the known coefficients:
Z = c0 + c1*X + c2*Y +c3*X*X + c4*X*Y + c5*Y*Y + c6*X**3 + c7*X**2*Y + ..... c26*X*Y**5 + c27*Y**6
After that you can plot it using matplotlib:
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
ax = plt.subplot(111, projection='3d')
ax.plot_surface( X, Y, Z )
plt.show()
来源：https://stackoverflow.com/questions/18088261/plotting-a-polynomial-in-python