Is there a tutorial for creating a hexbin heat map using Matplotlib?

Question

I'm trying to learn how to do a heatmap in Python using matplotlib. I'm going to be plotting a series of locations in a huge X,Y grid based off of an array of tuples. I found this code example which gives a perfect example of what I want to do. I can't seem to understand what the different parts of it mean though. Ultimately I want to output this on an overlay of an existing image. Thanks!

Answer 1

Nothing there is complicated. Anyway, here is a more simplified edition:

import pylab as pl
import numpy as np

n = 300                                     #number of sample data
x,y = np.random.rand(2,n)                   #generate random sample locations

pl.subplot(121)                             #sub-plot area 1 out of 2
pl.scatter(x,y,lw=0,c='k')                  #darw sample points
pl.axis('image')                            #necessary for correct aspect ratio

pl.subplot(122)                             #sub-plot area 2 out of 2

pl.hexbin(x,y,C=None,gridsize=15,bins=None,mincnt=1)        #hexbinning

pl.scatter(x,y,lw=0.5,c='k',edgecolor='w')  #overlaying the sample points
pl.axis('image')                            #necessary for correct aspect ratio

pl.show()                                   #to show the plot

Sample Points:

Hexbin result:

Note that mincnt=1 avoids plotting hexagon for empty cells. A hexagon cell with dark red has more number of sample points (here 5) inside. Dark blue hexagons have only one sample inside.