Split matrix into square cells

1 view (last 30 days)
A
A on 23 Apr 2022
Commented: A on 27 Apr 2022
I have a matirx 2-d matix where 1st colum is x and 2nd colum is y
[1 2
3 12
56 7;
4 5
6 5
6 8;
7 8
93 43
65 3;
7 8
93 43;]
I would like to spilt the data into square cells of 0.5m and know how many and what points are inside the cell
  2 Comments
Matt J
Matt J on 23 Apr 2022
What does "0.5m" signify? I suggest showing the desired output for your example.
A
A on 24 Apr 2022
0.5 is the dimenstions of the cell

Sign in to comment.

Accepted Answer

Voss
Voss on 23 Apr 2022
Edited: Voss on 24 Apr 2022
% (x,y) in units of m, presumably
xy = [1 2
3 12
56 7;
4 5
6 5
6 8;
7 8
93 43
65 3;
7 8
93 43;];
% define the grid starting at (min x, min y)-0.25, with spacing of 0.5:
x_grid = min(xy(:,1))-0.25:0.5:max(xy(:,1))+0.25;
y_grid = min(xy(:,2))-0.25:0.5:max(xy(:,2))+0.25;
% loop over grid cells:
for ii = 1:numel(x_grid)-1
for jj = 1:numel(y_grid)-1
% find points inside each cell:
idx = xy(:,1) >= x_grid(ii) & xy(:,1) < x_grid(ii+1) ...
& xy(:,2) >= y_grid(jj) & xy(:,2) < y_grid(jj+1);
if ~any(idx)
continue
end
% if some are found, print the info to the command line:
fprintf(1,'grid cell: x=%.2f->%.2f, y=%.2f->%.2f:',x_grid(ii+[0 1]),y_grid(jj+[0 1]));
fprintf(1,'%d point(s) inside: ',nnz(idx));
fprintf(1,'(%d,%d) ',xy(idx,:).');
end
end
grid cell: x=0.75->1.25, y=1.75->2.25:
1 point(s) inside:
(1,2)
grid cell: x=2.75->3.25, y=11.75->12.25:
1 point(s) inside:
(3,12)
grid cell: x=3.75->4.25, y=4.75->5.25:
1 point(s) inside:
(4,5)
grid cell: x=5.75->6.25, y=4.75->5.25:
1 point(s) inside:
(6,5)
grid cell: x=5.75->6.25, y=7.75->8.25:
1 point(s) inside:
(6,8)
grid cell: x=6.75->7.25, y=7.75->8.25:
2 point(s) inside:
(7,8) (7,8)
grid cell: x=55.75->56.25, y=6.75->7.25:
1 point(s) inside:
(56,7)
grid cell: x=64.75->65.25, y=2.75->3.25:
1 point(s) inside:
(65,3)
grid cell: x=92.75->93.25, y=42.75->43.25:
2 point(s) inside:
(93,43) (93,43)
  9 Comments
Voss
Voss on 27 Apr 2022
That's to get the first grid cell centered on the min x and min y (and I added 0.25 on the end so the grid completely spans the points). Without that, the count missed a couple of points due to them being right on the last edge of the grid, if I recall correctly.
A
A on 27 Apr 2022
Okay that makes more sense, thank you!

Sign in to comment.

More Answers (1)

Steven Lord
Steven Lord on 24 Apr 2022
Use the histcounts2 function.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!