Recreating a contour using coordinate points

Hi all,

I am reading contour points from an external file, which are not stored in order.

I want to set a start point and reconstruct the contour in counterclockwise direction.

I have the following code, it works when the points are equidistant and constructs the contour in clockwise direction.

How Can I change it in a way to force it in one direction so it will ignore the closest distance if the point in wrong direction?

Thanks a lot

%data=xlsread('known_point_set.xlsx'); 
startx=2;
starty=0;

data=[2 1;2 0;2 2;1 2;0 2;-1 2;-2 2;-2 -1;-2 -2;-1 -2;0 -2;-2 1;-2 0;-2 -1;-2 0;1 -2;2 -2;2 -1];

N = size(data,1);
idx=find(data(:,1)==startx & data(:,2)==starty);
data=circshift(data,N-idx+1,1);

dist = pdist2(data,data);

result = NaN(1,N);
result(1) = 1; % first point is first row in data matrix

for ii=2:N
    dist(:,result(ii-1)) = Inf;
    [~, closest_idx] = min(dist(result(ii-1),:));
    result(ii) = closest_idx;
end
newset=data(result,:);
plot(newset(:,1),newset(:,2))
xlswrite('screen.xlsx',newset);

Answer 1

[Rajesh Balagam]

You can try using a variant of Graham Scan algorithm:

https://en.wikipedia.org/wiki/Graham_scan