[Matplotlib-users] hexbin difference map

[Sebastian <se...@gm...>]

Any hints on how to visualize the density difference between two hexbin
plot, each with x-y (2D) data?

Each set has roughly 300,000 points.
The range in x and y values for each data set are roughly similar but with
slightly different density:
range x,x1: -1.222 to 3.656
range y,y1: 13.191, 18.150

So the steps:

(1) Produce the two hexbin maps:

fig1=hexbin(c_b204_jmk,c_b204_k,C = None, gridsize = 100, bins = None,
xscale = 'linear', yscale = 'linear', cmap=None, norm=None, vmin=None,
vmax=None, alpha=None, linewidths=None, edgecolors='none',reduce_C_function
= np.mean, mincnt=None, marginals=False)

fig2=hexbin(c_b211_jmk,c_b211_k,C = None, gridsize = 100, bins = None,
xscale = 'linear', yscale = 'linear', cmap=None, norm=None, vmin=None,
vmax=None, alpha=None, linewidths=None, edgecolors='none',reduce_C_function
= np.mean, mincnt=None, marginals=False)

(2) Determine the difference in the hexbin counts, with

diff_hex=fig2.get_array()-fig1.get_array()


(3) BUT when i try to plot the diff hexbin map

fig3=hexbin(c_b211_jmk,c_b211_k,C = diff_hex, gridsize = 100, bins = None,
xscale = 'linear', yscale = 'linear', cmap=None, norm=None, vmin=None,
vmax=None, alpha=None, linewidths=None, edgecolors='none',reduce_C_function
= np.mean, mincnt=None, marginals=False)

I obviously get a:
IndexError: index out of bounds

Because:
len(c_b211_jmk) = len(c_b211_k)  != len(diff_hex),
Since diff_hex are the binned counts.

(4) Any simple way to get around this, to plot the hexbin difference counts
on top of the the  hexbin (c_b211_jmk,c_b211_k) distribution?

thanks in advance & with best regards,
- Sebastian