Convex Hull algorithm without built-in function
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I have found on mathworks a convex hull algorithm, which uses randomly defined vectors as an input. I have tried to change random vectors to another ones, which I want to use. Unfortunately, the program says 'indeces on the right sight are not compatible with indeces on left side', giving me error at ind(1) = find(V == P1(:,1));
And I don't know what I need to change to make this program work with user-defined vectors, not random ones. So, I would be very glad for any help with this question.
x = random('Normal',0,1,1,10);
y = random('Normal',0,1,1,10);
InputData = [x',y'];
[V,I,vertices] = ConvexHull(InputData);
figure(46)
plot(InputData(:,1),InputData(:,2),'.','Color','red');
hold on
plot(V(:,1),V(:,2),'Marker','^','LineStyle','--','Color','#7E2F8E')
title('SuperOutput');
xlabel('x');
ylabel('y');
legend('InputData','Convex hull');
function [V,I,n] = ConvexHull(InputData)
V = [InputData(1:3,:)]; I = [1:3]';
for k = 4:length(InputData)
pk = InputData(k,:);
sup_ver = [];
ind = [];
index = [];
for i = 1:length(V)
vi = V(i,:);O = [];
for j = 1:length(V)
if (i ~= j)
vj = V(j,:);
O(j) = det([1,pk;1,vi;1,vj]);
end
end
O(O == 0) = [];
if ((numel(unique(sign(O))) == 1) == 1)
sup_ver = [sup_ver;vi];
end
end
if (isempty(sup_ver) == 0)
P1 = sup_ver(1,:);
P2 = sup_ver(2,:);
P3 = pk;
s = det([P1 - P2;P3 - P1]);
n = 1;
while (n <= length(V))
P = V(n,:);
if ((P ~= P1) & (P ~= P2) & (P ~= pk) & ((s * det([P3 - P;P2 - P3]) >= 0) & (s * det([P1 - P;P3 - P1]) >= 0) & (s * det([P2 - P;P1 - P2]) >= 0)) == 1)
V(n,:) = [];
I(n) = [];
n = n - 1;
end
n = n + 1;
end
ind(1) = find(V == P1(:,1));
ind(2) = find(V == P2(:,1));
index = find(InputData == pk(:,1));
if (ind(2) - ind(1) == 1)
V = [V(1:ind(1),:);pk;V(ind(1) + 1:end,:)];
I = [I(1:ind(1));index;I(ind(1) + 1:end)];
else
V = [pk;V];
I = [index;I];
end
end
end
V = vertcat(V,V(1,:));
I = vertcat(I,I(1));
end
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