Python hexbin plot with 2D function

May 6, 2024

I’m trying to display a two dimensional function on a hexagonal grid with pyplot.hexbin but it only produces a line and ignores the rest of the function. How do I solve this?

def func(x,y):
    return x*2+y*2

x = np.linspace((-0.5)/4*5, (0.5)/4*5, int(2e3))   
y = np.linspace(-0.5, 0.5, int(2e3))    

plt.hexbin(x,
           y,
           func(x,y), 
           gridsize=(8,4),
           cmap='gnuplot')
plt.show()

enter image description here

>Solution :

The func(x,y) function returns a scalar value for each (x, y) pair, but hexbin expects x and y to be arrays of the same length representing coordinates. Input another array Z with the scalar values which will be the colours of each hex.
Try:

import numpy as np
import matplotlib.pyplot as plt

def func(x,y):
    return x*2+y*2

x = np.linspace((-0.5) / 4 * 5, (0.5) / 4 * 5, int(2e3))
y = np.linspace(-0.5, 0.5, int(2e3))
X, Y = np.meshgrid(x, y)

# Evaluate the function for each combination of x and y
Z = func(X, Y)

plt.hexbin(X.flatten(),    # Flatten X and Y to 1D arrays
           Y.flatten(),
           C=Z.flatten(),  # Flatten Z to 1D array for color values
           gridsize=(8, 4),
           cmap='gnuplot')

plt.show()

You can also add a colorbar before the show like: