Re: [Matplotlib-users] hexbin difference map

[Erik T. <eri...@gm...>]

Just do something like this:

newx = concatenate((c_b211_jmk,c_b204_jmk))
newy = concatenate((c_b211_k, c_b204_k))
newc = concatenate((ones(c_b211_k.size),-1*ones_like(c_b204_k.size)))

hexbin(newx,newy,C=newc,reduce_C_function=np.sum)

Then the color coding in each bin should be the number of counts from
b211 - number of counts from b204.


On Fri, May 18, 2012 at 12:11 PM, Sebastian <se...@gm...> wrote:
> 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



-- 
Erik Tollerud