count 3D points to construct 3D voxel plot

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hahaha_hahaha
hahaha_hahaha 2015-9-12
评论： hahaha_hahaha 2015-9-12
I am using MATLAB R2015a on OSX 10.10.5. I would like to count number of points in a 3D grid and plot the voxel color coded with the counts. However my code produced a voxel plot that is not consistent with a scattered plots of my data (attached). I have high voxel counts in regions with few data points. Could you point out my error? Thank!
load data
bins = 20;
xedge = linspace(min(data(:,1)),max(data(:,1))+1e14*eps,bins);
yedge = linspace(min(data(:,2)),max(data(:,2))+1e14*eps,bins);
zedge = linspace(min(data(:,3)),max(data(:,3))+1e14*eps,bins);
loc = zeros(size(data));
len = length(xedge)-1;
mid = zeros(len,3);
for i = 1:len
mid(i,1) = (xedge(i)+xedge(i+1))/2;
mid(i,2) = (yedge(i)+yedge(i+1))/2;
mid(i,3) = (zedge(i)+zedge(i+1))/2;
end
[~,loc(:,1)] = histc(data(:,1),xedge);
[~,loc(:,2)] = histc(data(:,2),yedge);
[~,loc(:,3)] = histc(data(:,3),zedge);
hasdata = all(loc>0,2);
sz(1:3) = len;
cnt = accumarray(loc(hasdata,:),1,sz);
figure
subplot(1,2,1)
scatter3(data(:,1),data(:,2),data(:,3))
view(3)
subplot(1,2,2)
[x,y,z] = meshgrid(mid(:,1),mid(:,2),mid(:,3));
[~,I] = max(cnt(:));
[xi,yi,zi] = ind2sub(size(cnt),I);
slice(x,y,z,cnt,mid(xi,1),mid(yi,2),mid(zi,3),'nearest')
view(3)

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采纳的回答

Walter Roberson
Walter Roberson 2015-9-12
Your code appears to be well designed.
What I notice when I test with your code is that the slice output appears to be the mirror of the scatter output along the y axis. I am not sure why that is at the moment, but try
slice(x,y,z,permute(cnt,[2 1 3]),mid(xi,1),mid(yi,2),mid(zi,3),'nearest')
If that works for you then the explanation would be rooted in the fact that for matrices, x is the columns and y is the rows

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