anticlockwise points coordinates sorting
显示 更早的评论
Hi,
I have the follwoing points cooridnates:
A = [0 0 ;
1 0.2;
0 1 ;
0 0.6;
1 0 ;
1 1 ;
0.6 1;
0.2 0;
0 0 ;
0.2 1;
0 0.2;
0.6 0;
1 0.6];
I would like to sort these points in a way that they resmbles points on a square polygon in an anticloskwise direction, as follwoing:
B = [0 0 ;
0.2 0;
0.6 0;
1 0 ;
1 0.2;
1 0.6;
1 1 ;
0.6 1;
0.2 1;
0 1 ;
0 0.6;
0 0.2;
0 0];
%here is how to visulaise the points
figure;
plot(A(:,1),A(:,2),'rx','LineWidth',2)
Any idea how to sort/arrange these points?
Thanks.
采纳的回答
A = [0 0 ;
1 0.2;
0 1 ;
0 0.6;
1 0 ;
1 1 ;
0.6 1;
0.2 0;
0 0 ;
0.2 1;
0 0.2;
0.6 0;
1 0.6];
c = [mean(A(:,1)), mean(A(:,2))]; % centroid of the points
d = A - c; % vectors from points to centroid
angles = atan2d(d(:,1), d(:,2)); % angles from centroid to each point
[~,idx] = sort(angles, 'descend'); % sort the angles anti-clockwise
B = A(idx, :) % sort the points based on the angles
plot(B(:,1),B(:,2), 'rx')
grid on
hold on
text(B(:,1), B(:,2), sprintfc('%d', 1:numel(idx)))
plot(c(1), c(2), 'bo')
6 个评论
Thanks. Clearly the method you presented works, but the points that spread on the bottom edge, i.e., 
and 
are not on the top of the 2D matrix. half of them are at the bottom. I understand that one way to correct this is to shift these points, but is there a generic solution that lay the points coordinates correctly together based on their edges (the points on the first (bottom) edge are on the top of the matrix, then the points on the second (right) edge, and so on so forth)?
and are not on the top of the 2D matrix. half of them are at the bottom. I understand that one way to correct this is to shift these points, but is there a generic solution that lay the points coordinates correctly together based on their edges (the points on the first (bottom) edge are on the top of the matrix, then the points on the second (right) edge, and so on so forth)?Try this
A = [0 0;
1 0.2;
0 1;
0 0.6;
1 0;
1 1;
0.6 1;
0.2 0;
0 0;
0.2 1;
0 0.2;
0.6 0;
1 0.6];
c = [mean(A(:,1)), mean(A(:,2))]; % centroid of the points
d = A - c; % vectors from points to centroid
angles = atan2d(d(:,2), d(:,1)); % angles from centroid to each point
angles(angles<-135) = angles(angles<-135) + 360; % offset so the [0, 0.2] point will be last
[~,idx] = sort(angles); % sort the angles
B = A(idx, :) % sort the points based on the angles
plot(B(:,1),B(:,2), 'rx')
grid on
hold on
text(B(:,1), B(:,2), sprintfc('%d', 1:numel(idx)))
plot(c(1), c(2), 'bo')
Les Beckham
2022-11-22
You're welcome.
Have you tried applying this approach to other "polygons"? I suspect that it will work for anything that is similar to this example.
If this answer solved your original problem I would appreciate it if you click the "Accept this answer" button.
LH
2022-11-22
Les Beckham
2022-11-22
You are quite welcome.
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Operating on Diagonal Matrices 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
