Code covered by the BSD License

Download apps, toolboxes, and other File Exchange content using Add-On Explorer in MATLAB.

### Highlights from histograms for ND data

5.0
5.0 | 1 rating Rate this file 2 Downloads (last 30 days) File Size: 2.44 KB File ID: #31889 Version: 1.0

# histograms for ND data

### Diederick (view profile)

Create histograms for ND data using ND bins

File Information
Description

histnd Histogram count of ND data with ND bins

histmat = histnd(x, y, ..., xedges, yedges, ...)
Extract ND histogram data containing the number of events
of [x, y, ...] tuples that fall in each bin of the ND-grid defined by
xedges, yedges, .... The edges are passed to histc internally and should
therefore conform to histc's input restrictions: the edge-vectors should
be monotonically non-decreasing.

[histmat, nOOF, OOFidx] = histnd(x, y, ..., xedges, yedges, ...)
If any values are outside of the range of the edges, they are not
counted. The number of those cases and their linear index in the input
data is however returned in the second and third output arguments.

EXAMPLES

events = 1000000;
x1 = sqrt(0.05)*randn(events,1)-0.5; x2 = sqrt(0.05)*randn(events,1)+0.5;
y1 = sqrt(0.05)*randn(events,1)+0.5; y2 = sqrt(0.05)*randn(events,1)-0.5;
x= [x1;x2]; y = [y1;y2];

For linearly spaced edges:
xedges = linspace(-1,1,64); yedges = linspace(-1,1,64);
histmat = histnd(x, y, xedges, yedges);
figure; pcolor(xedges,yedges,histmat'); colorbar ; axis square tight ;

For nonlinearly spaced edges:
xedges_ = logspace(0,log10(3),64)-2; yedges_ = linspace(-1,1,64);
histmat_ = histnd(x, y, xedges_, yedges_);
figure; pcolor(xedges_,yedges_,histmat_'); colorbar ; axis square tight ;

3D data
x = 3.*randn(640000,1);
y = 1.*randn(640000,1);
z = 1.*randn(640000,1);
histmat = histnd(x,y,z,linspace(min(x),max(x),20),linspace(min(y),max(y),20),linspace(min(z),max(z),20));
% make 3D hist, color of points indicates count
[xp,yp,zp] = meshgrid(linspace(min(x),max(x),20),linspace(min(y),max(y),20),linspace(min(z),max(z),20));
% cut away histogram positions where count is 0
qzero = histmat==0;
histmat(qzero) = [];
xp(qzero) = [];
yp(qzero) = [];
zp(qzero) = [];
% draw points
figure;%('Renderer','OpenGL') % might need the openGL renderer to handle so many points
ax = scatter3(xp(:),yp(:),zp(:),'.');
% color them according to count
cdata = histmat(:)./max(histmat);
set(ax,'CData',cdata);
xlabel('X'), ylabel('Y'), zlabel('Z')

Acknowledgements

2 D Histogram Calculation inspired this file.

MATLAB release MATLAB 7.12 (R2011a)
Other requirements MATLAB r2009b or later is needed due to use of tilde syntax (http://blogs.mathworks.com/loren/2009/09/11/matlab-release-2009b-best-new-feature-or/). The function will work on older MATLABs by replacing the tilde on line 79 with a dummy variable
Tags for This File   Please login to tag files.