Data density plot

Plots data density of a two-dimensional distribution for human viewing.

Description

Data density can be hard to read from scatter plots due to overstriking. I therefore calculate data density at each pixel as the reciprocal of the sum of squared distance from each point, adding a fudge factor to prevent points actually within the pixel going to infinity.

The resulting plot allow for a visual fix on data density.

• MATLAB release: MATLAB 7.9 (2009b)

[bmv]

Replace this part "for kk = 1: length(x)"
to this:
"parfor kk = 1: length(x)"
This will help speed up the computation for multicore systems after running matlabpool.

[Alexander Kosenkov]

 

[J G]

Good function! Would it work for one-dimensional data, ie. a vector? I am using hist(Y) but would prefer to show the density like this... Thanks!

[Malcolm McLean]

J G. Yes. Just pass in a dimension of one pixel for the y axis, and it ought to provide you with a data density plot. You'll have to stretch the image to see it.

[Jason Kaeding]

Very slow. Don't replace the kk loop with parfor as bmv suggests, just vectorize the calculation and get rid of the loop:

dmap(ii+1, jj+1) = sum( 1./ ( (x - xi).^2 + (y - yi).^2 + fudge) );

The other loops can be vectorized as well if you use bsxfun.

[Mehdi Moghaddam]

super slow:(

[Ben Ruppel]

Great tool, but maybe it should flip the y-axis so the results aren't upside down. Also, Matlab stays frozen in a busy state as long as the result figure is open. Need to close the figure before I can do anything else.