CODEWITHSUNDEEP
matlabconvex-hull
Zoidberg Alpha
Zoidberg Alpha

Reputation: 25

Matlab Convhull Error. Not enough unique data point

I have been receiving this error in Matlab when I tried to calculate the convex hull of a set of numbers inscribed by a circle. Here is the code, and the error I kept getting is: Error computing the convex hull. Not enough unique points specified.

for u = 1:50; 
  for v = 1:50;       
    if sqrt(((u-25)^2)+((v-25)^2)) <= 25
      c = convhull(u,v);
      plot(u(c),v(c),'r-',u,v,'b*')         
    end
  end
end

Points inscribed or on a circle: enter image description here

Upvotes: 1

Views: 1690

Answers (1)

jodag
jodag

Reputation: 22234

In your code you are sending individual points to convhull. Instead determine all the points in the set first, then send them all to the function at once. Here's an example.

% create mesh
[u,v] = meshgrid(1:50,1:50);
% get indicies of points within the circle
idx = sqrt((u-25).^2+(v-25).^2) <= 25;
% filter outside points
u = u(idx);
v = v(idx);
% compute convex hull
c = convhull(u,v);
plot(u(c),v(c),'r-',u,v,'b.');

Results

enter image description here

Side note: Formally a singleton set is convex thus it's its own convex hull. I'm not sure why MathWorks decided to return an error in this case.

Upvotes: 1

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