How to find number of points in 3d gridded data
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I have a large dataset of 3D points (x,y,z) and need to divide them into a regular grid of voxel and to count the number of points that fall into each voxel. Because the dataset is very large I need to use some efficient built-in function and avoid to iterate along each cell comparirg the coordinates.
How can I create a 3D grid of voxels? How can I compute the number of points for each cell?
Any help it is appriciate. Thanks in advance
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saumya jayasundara
2018-6-12
编辑:Cedric
2018-6-13
prompt='What is the threshould value for cell size?'; T=input(prompt);
load('Point2.mat');
[m,n] = size(Point);
count=1;
Xmax=Point(count,1);
Xmin=Point(count,1);
Ymax=Point(count,2);
Ymin=Point(count,2);
while count< m
count=count+1;
if Xmax<Point(count,1)
Xmax=Point(count,1);
end
if Xmin>Point(count,1)
Xmin=Point(count,1);
end
if Ymax<Point(count,2)
Ymax=Point(count,2);
end
if Ymin>Point(count,2)
Ymin=Point(count,2);
end
end
Xmax;
Xmin;
Ymax;
Ymin;
corner1=[Xmin,Ymin];
corner2=[Xmax,Ymin];
corner3=[Xmax,Ymax];
corner4=[Xmin,Ymax];
cellx = floor(((Xmax-Xmin)/T)+T);
celly = floor(((Ymax-Ymin)/T)+T);
cell= zeros(cellx,celly);
cellcount=1;
for ycount = 1:celly
for pcount = 1:cellx
cell(pcount,ycount)= cellcount;
cellcount=cellcount+1;
end
end
attribute1=zeros(m,2);
Point=[Point(:,1:3) attribute1];
'Devide Grid'
%for cellcount2= 1:cellcount
for xcount= 1:m
if Point(xcount,4)==0
for cellxc =1:cellx
l=cellxc*T;
if(Xmin+l-T)<=Point(xcount,1)
if Point(xcount,1)<(Xmin+l)
for cellyc= 1:celly
k=cellyc*T;
if (Ymin+k-T)<=Point(xcount,2)
if Point(xcount,2)<(Ymin+k)
Point(xcount,4)=cell(cellxc,cellyc);
break
else
continue
end
else
continue
end
end
else
continue
end
else
continue
end
end
else
continue
end
end
'Devided'
%Point(1:100,:)
%file=fopen('point.txt','w');
%fprintf(file,Point);
%sum=0;
%sumdiv=0;
%for cellcnt= 1:cellcount
% for Pcount2=1:m
% if Point(Pcount2,4)==cellcnt
% sum=sum+Point(Pcount2,3);
% sumdiv=sumdiv+1;
% else
% continue
% end
%end
%avg=sum/sumdiv;
%for Pcount2=1:m
% if Point(Pcount2,4)==cellcnt
% Point(Pcount2,5)=avg;
% else
% continue
%end
%end
%end
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