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weighted 2D histogram
From: |
lynx . abraxas |
Subject: |
weighted 2D histogram |
Date: |
Sat, 19 Dec 2009 13:11:32 +0100 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
Hello!
Some time ago I found the code below to create a 2D-histogram of a 2D point
set.
Now I need a weighted version of this such that each cell of the 2D-histogram
is not just the amount of points in that cells area but the sum of all weights
that come with the points that ly in that cell.
So I have some thing like [vY, vX, vW] and want in each output cell value to
be the sum of vW of all the points [vY, vX] inside that cell. The code below
would then be a specialization where vW==1 for all points.
Can someone give me some help or hint on how to realize this?
Thanks,
Lynx
%function mHist = hist2d ([vY, vX], vYEdge, vXEdge)
%2 Dimensional Histogram
%Counts number of points in the bins defined by vYEdge, vXEdge.
%size(vX) == size(vY) == [n,1]
%size(mHist) == [length(vYEdge) -1, length(vXEdge) -1]
%
%EXAMPLE
% mYX = rand(100,2);
% vXEdge = linspace(0,1,10);
% vYEdge = linspace(0,1,20);
% mHist2d = hist2d(mYX,vYEdge,vXEdge);
%
% nXBins = length(vXEdge);
% nYBins = length(vYEdge);
% vXLabel = 0.5*(vXEdge(1:(nXBins-1))+vXEdge(2:nXBins));
% vYLabel = 0.5*(vYEdge(1:(nYBins-1))+vYEdge(2:nYBins));
% pcolor(vXLabel, vYLabel,mHist2d); colorbar
function mHist = hist2d (mX, vYEdge, vXEdge)
nCol = size(mX, 2);
if nCol < 2
error ('mX has less than two columns')
end
nRow = length (vYEdge)-1;
nCol = length (vXEdge)-1;
vRow = mX(:,1);
vCol = mX(:,2);
mHist = zeros(nRow,nCol);
for iRow = 1:nRow
rRowLB = vYEdge(iRow);
rRowUB = vYEdge(iRow+1);
vColFound = vCol((vRow > rRowLB) & (vRow <= rRowUB));
if (~isempty(vColFound))
vFound = histc (vColFound, vXEdge);
nFound = (length(vFound)-1);
if (nFound ~= nCol)
disp([nFound nCol])
error ('hist2d error: Size Error')
end
[nRowFound, nColFound] = size (vFound);
nRowFound = nRowFound - 1;
nColFound = nColFound - 1;
if nRowFound == nCol
mHist(iRow, :)= vFound(1:nFound)';
elseif nColFound == nCol
mHist(iRow, :)= vFound(1:nFound);
else
error ('hist2d error: Size Error')
end
end
end
- weighted 2D histogram,
lynx . abraxas <=