How to find number of points in 3d gridded data

Question

DP87 2017-12-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/371548-how-to-find-number-of-points-in-3d-gridded-data

编辑： Cedric 2018-6-13

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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Answer 1

saumya jayasundara 2018-6-12

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/371548-how-to-find-number-of-points-in-3d-gridded-data#answer_324300

编辑：Cedric 2018-6-13

在 MATLAB Online 中打开

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