4 views (last 30 days)
Show older comments
Aravin on 31 Jan 2022
-
-
Link
Direct link to this question
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels
Commented: Turlough Hughes on 1 Feb 2022
Accepted Answer: Turlough Hughes
Open in MATLAB Online
Dear all,
I have 3D locations in three vectors, x, y, and z. I want to divide the space into fix numbe of grids lets say 2 x 2 x 2. Lets take example in 2D space. I have two vectors x, and y, as below;
x = [1 1 2 2 3 10];
y = [1 2 1 1 2 5];
plot(x,y, '+')
now I divide in to 2 x 2. So the interval for x would be 0-to-5 and then 5.1-to-10, and likewise for y(0-to-2.5, and 2.6-to-5). I have drawn the points and divided the space manually as shown below.
now the there are four cells. I have vector r that should be r = [3,3,3,3,3,2] where all points are in cell 3 and only point 5,10 is on cell 2.
0 Comments Show -2 older commentsHide -2 older comments
Show -2 older commentsHide -2 older comments
Sign in to comment.
Sign in to answer this question.
Accepted Answer
Turlough Hughes on 31 Jan 2022
Open in MATLAB Online
Example in 2D
% Data
x = rand(1,100)*10;
y = rand(1,100)*5;
r = zeros(size(x)); % group index
r(x>0 & x<=5 & y>0 & y<=2.5) = 1;
r(x>5 & x<=10 & y>0 & y<=2.5) = 2;
r(x>0 & x<=5 & y>2.5 & y<=5) = 3;
r(x>5 & x<=10 & y>2.5 & y<=5) = 4;
figure(), gscatter(x,y,r)
hold on, axis padded, legend off
xline(5), yline(2.5)
Here I'm using conditions > as well as <= so that you can select one edge, eg 5 instead of switching between 5 and 5.1 etc, though if you need to modify from this then do so as required.
Example in 3D
% Additional data for z
z = rand(1,100)*5;
% E for Edges
xE = [0 5 10];
yE = [0 2.5 5];
zE = [0 2.5 5]; % You can see why just one value for the edge is useful.
% Group the data according to the edges (r gives the groups).
idx = 1;
for ii = 1:numel(xE)-1
for jj = 1:numel(yE)-1
for kk = 1:numel(zE)-1
r(x>xE(ii) & x<=xE(ii+1) & y>yE(jj) & y<=yE(jj+1) & z>zE(kk) & z<=zE(kk+1)) = idx;
idx = idx + 1;
end
end
end
cmap = jet(8);
figure(), scatter3(x,y,z,80,cmap(r,:),'filled')
Not the best visualisation but you can see that it does the job.
6 Comments Show 4 older commentsHide 4 older comments
Show 4 older commentsHide 4 older comments
Aravin on 1 Feb 2022
Direct link to this comment
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels#comment_1964075
Thank you Huges. Wonderfull. As I stated, the grid size which we have kept 2 x 2 or 2 x 2 x 2 is just an example. Could you please help in making n x n or n x n x n ? As I have to experiment with different values of n.
Your support is highly appreciated on this.
Turlough Hughes on 1 Feb 2022
Direct link to this comment
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels#comment_1964170
Open in MATLAB Online
Just use linspace to define your edges, for example:
% Data
x = rand(1,1000)*10;
y = rand(1,1000)*5;
z = rand(1,1000)*5;
r = zeros(size(x)); % group index
% E for Edges
n = 3;
xE = linspace(min(x)-1e-6, max(x), n+1);
yE = linspace(min(y)-1e-6, max(y), n+1);
zE = linspace(min(z)-1e-6, max(z), n+1);
% Group the data according to the edges
idx = 1;
for ii = 1:numel(xE)-1
for jj = 1:numel(yE)-1
for kk = 1:numel(zE)-1
r(x>xE(ii) & x<=xE(ii+1) & y>yE(jj) & y<=yE(jj+1) & z>zE(kk) & z<=zE(kk+1)) = idx;
idx = idx + 1;
end
end
end
cmap = colorcube(n^3);
figure(), scatter3(x,y,z,200,cmap(r,:),'filled')
Aravin on 1 Feb 2022
Direct link to this comment
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels#comment_1964180
Thank you so much. Please illusarate in 2D too. sorry for being naive.
Turlough Hughes on 1 Feb 2022
Direct link to this comment
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels#comment_1964200
Open in MATLAB Online
% Data
x = rand(1,500)*10;
y = rand(1,500)*5;
r = zeros(size(x)); % group index
% E for Edges
n = 6;
xE = linspace(min(x)-1e-6, max(x), n+1);
yE = linspace(min(y)-1e-6, max(y), n+1);
% Group the data according to the edges
idx = 1;
for ii = 1:numel(xE)-1
for jj = 1:numel(yE)-1
r(x>xE(ii) & x<=xE(ii+1) & y>yE(jj) & y<=yE(jj+1)) = idx;
idx = idx + 1;
end
end
cmap = colorcube(n^2);
figure(), scatter(x,y,100,cmap(r,:),'filled')
xline(xE)
yline(yE)
Aravin on 1 Feb 2022
Direct link to this comment
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels#comment_1964280
What version of matlab you are using? I don't have xline in 2018.
Turlough Hughes on 1 Feb 2022
Direct link to this comment
https://jmaab.mathworks.com/matlabcentral/answers/1639770-divide-the-3d-feature-space-into-grid-and-then-get-their-labels#comment_1964300
The xline() and yline() functions were introduced in 2018b.
Sign in to comment.
More Answers (0)
Sign in to answer this question.
See Also
Categories
MATLABGraphics2-D and 3-D Plots
Find more on 2-D and 3-D Plots in Help Center and File Exchange
Tags
- 2d
- 3d
- handles
Products
- MATLAB
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
An Error Occurred
Unable to complete the action because of changes made to the page. Reload the page to see its updated state.
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
You can also select a web site from the following list
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- Deutsch
- English
- Français
- United Kingdom(English)
Asia Pacific
- Australia (English)
- India (English)
- New Zealand (English)
- 中国
- 日本Japanese (日本語)
- 한국Korean (한국어)
Contact your local office
