python - map a hexagonal grid in matplotlib

Question

I'm wanting to draw a figure with a hexagonal grid. The end result should look like a honeycomb. However, I'm having trouble getting my hexagons sized correctly using matplotlib.collections.RegularPolyCollection. Can anyone see what I am doing wrong, or offer another solution. I imagine this has been done before, so no need for me to reinvent the wheel.

import matplotlib.pyplot as plt
from matplotlib import collections, transforms
from matplotlib.colors import colorConverter
import numpy as np

# Make some offsets, doing 4 polygons for simplicity here
xyo = [(0,0), (1,0), (0,1), (1,1)]
# length of hexagon side
hexside = 1
# area of circle circumscribing the hexagon
circ_area = np.pi * hexside ** 2

fig, ax = plt.subplots(1,1)
col = collections.RegularPolyCollection(6, np.radians(90), sizes = (circ_area,),
    offsets=xyo,transOffset=ax.transData)
ax.add_collection(col, autolim=True)
colors = [colorConverter.to_rgba(c) for c in ('r','g','b','c')]
col.set_color(colors)
ax.autoscale_view()
plt.show()

For what it's worth, I think your confusion is because the size/area specified by sizes is in points, rather than data coordinates. However, an easier route for what you're doing is probably to exploit hexbin. — Joe Kington

alexkaz alexkaz · Accepted Answer · 2020-10-11T08:43:20

Whoever struggles with the same issue in 2020+, check out my hexalattice module: It allows to create hexagonal grids (hexagonal lattices) in 2D with fine control over spatial distribution of the hexagons, circular clop of the lattice and rotations around the central slot.

Usage and graphical output:

from hexalattice.hexalattice import *
hex_centers, _ = create_hex_grid(nx=10,
                                 ny=10,
                                 do_plot=True)
plt.show()    # import matplotlib.pyplot as plt

Installation:

'>> pip install hexalattice'

Advanced features

The module allows stacking of few grids, arbitrary grid rotation around its center, advanced control over gaps between the hexagons etc.

Example:

hex_grid1, h_ax = create_hex_grid(nx=50,
                              ny=50,
                              rotate_deg=0,
                              min_diam=1,
                              crop_circ=20,
                              do_plot=True)
create_hex_grid(nx=50,
                ny=50,
                min_diam=1,
                rotate_deg=5,
                crop_circ=20,
                do_plot=True,
                h_ax=h_ax)

python - map a hexagonal grid in matplotlib

1 Answers