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If I have points in a graph in matlab that are randomly sorted and when plotted produce various closed shapes. Given a specific point on the left side of one of the closed shapes how can I get all the points of that shape in a vector form keeping in mind the convention of collecting the points is moving in a clockwise direction.

Nermeen Ahmed
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  • Maybe this [question/answer](http://stackoverflow.com/questions/11631934/sort-coordinates-points-in-matlab) is helpful to you? – Schorsch May 22 '13 at 14:20
  • Or [this code from Matlab Central](http://www.mathworks.com/matlabcentral/fileexchange/35488-connect-randomly-ordered-2d-points-into-a-minimal-nearest-neighbor-closed-contour)? – Schorsch May 22 '13 at 14:21

1 Answers1

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A commented example:

cla
% Random data
x = rand(15,1);
y = rand(15,1);
scatter(x,y)
% Random point to the left
hold on
p = [-0.1, rand(1)*0.2 + 0.5];
plot(p(1),p(2),'*r')

% Separate points that lie above your point
idx = y >= p(2);

% Sort x then y increasing for upper half and x then y decreasing for lower half 
shape = [sortrows([x( idx) y( idx)],[1 2]) 
         sortrows([x(~idx) y(~idx)],[-1 -2])];

Check that shape contains clockwise sorted coordinates by plotting an open line:

% Plot clockwise open line
plot(shape(1:end ,1),shape(1:end,2),'k')

enter image description here

Oleg
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