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pythonnumpymatplotlibplot
SolessChong
SolessChong

Reputation: 3407

Python show a two-dimensional PDF function

Is there any elegant way of showing a two-dimensional PDF function?

I have a function F(x,y) and I want to illustrate it.

Here is one solution:

Generate a meshgrid and calculate the value of each point, then use imshow()

     1 1.5   2 2.5   3 3.5
    -----------------------
  1| 0   0 0.1 0.2 0.3 0.5
1.5| 0 0.1 0.2 0.3 0.4 0.8
  2| 0 0.1 0.2 0.3 0.5 0.8
2.5| 0 0.2 0.2 0.4 0.4   1
  3| 0 0.1 0.2 0.3 0.5 0.8

However I don't know whether to use np.vstack or np.meshgrid to generate the "meshgrid".

Can anybody tell me how to draw the map above? Or provide a more "elegant" way to do it?

Feedback

The solution below works perfect. It yields the figure like this: Distribution

Upvotes: 4

Views: 1969

Answers (1)

wim
wim

Reputation: 362756

You can use meshgrid to make the coordinates:

import numpy as np
x = np.linspace(1, 3.5, 6)
y = np.linspace(1, 3, 5)
X, Y = np.meshgrid(x, y)

And then apply your F at each point:

z = np.array([F(x,y) for x,y in zip(np.ravel(X), np.ravel(Y))])
Z = z.reshape(X.shape)

Now create a surface plot something like this:

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.plot_surface(X, Y, Z)
ax.set_xlabel('X')
ax.set_ylabel('Y')
ax.set_zlabel('F(X, Y)')
plt.show()

You can of course use imshow aswell, if you prefer to represent the F using colour rather than using a 3D plot. It doesn't make much sense to use meshgrid if you're going to use imshow though.

Upvotes: 3

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