function hist2D ( X, NBins, Smooth, N )

%
%  function [ H ] = hist2D ( X, NBins, Smooth )
%
%  Computes and display a 2D histogram. The axes will be set such that
%  all data points are visible.
%
%  Input
%
%  	X	2 x N		Matrix of data points. Points are stored
%				as columns
%
%	NBins	2 x 1		Number of bins in each dimension
%
%	Smooth	scalar		Size of smoothing kernel used as Parzen window
%
%       N       scalar		Number of contour lines to be drawn.
%
%
%  (c) in 1998 by California Institute of Technology
%
%  Markus Weber
%

%
%  $Log: hist2D.m,v $
%  Revision 1.1  1999/05/05 21:14:40  mweber
%  Minor changes.
%
%  Revision 1.2  1999/05/05 21:07:01  mweber
%  Complete overhaul.
%
%  Revision 1.1.1.1  1999/05/05 17:50:09  mweber
%  Initial import
%		
 
H = zeros(NBins(2), NBins(1));

xMin = min(X(1, :));
xMax = max(X(1, :));

yMin = min(X(2, :));
yMax = max(X(2, :));

dX = (xMax - xMin) / (NBins(1) - 1);
dY = (yMax - yMin) / (NBins(2) - 1);

BX = 1 + floor((X(1, :) - xMin) / dX + 0.5);
BY = 1 + floor((X(2, :) - yMin) / dY + 0.5);

for i = 1 : size(X, 2),

	H(BY(i), BX(i)) = H(BY(i), BX(i)) + 1;
end

H = gaussN(H, Smooth);

[XX YY] = meshgrid(xMin : dX : xMax, yMin : dY : yMax);

contour(XX, YY, H, N);

axis('image');