How can I find the set of vertices of hexagons which are adjacent to a random point?

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I have a set of hexagons whose blue coordinates are known:
I have a random red point and I need to know the 4 (in some cases it would be 3) points which are immediately adjacent to it. These points are contained in the black box shown for illustration.
I tried to sort the blue points by measuring distances but I keep getting extra points (shown by black arrows) or missing the required points.

Respuesta aceptada

Matt J
Matt J el 13 de Ag. de 2024
Editada: Matt J el 13 de Ag. de 2024
hex=[ 0 -1.0000
-0.8660 -0.5000
-0.8660 0.5000
0 1.0000
0.8660 0.5000
0.8660 -0.5000
1.7321 -1.0000
0.8660 -0.5000
0.8660 0.5000
1.7321 1.0000
2.5981 0.5000
2.5981 -0.5000
3.4641 -1.0000
2.5981 -0.5000
2.5981 0.5000
3.4641 1.0000
4.3301 0.5000
4.3301 -0.5000] %hexagon points
hex = 18x2
0 -1.0000 -0.8660 -0.5000 -0.8660 0.5000 0 1.0000 0.8660 0.5000 0.8660 -0.5000 1.7321 -1.0000 0.8660 -0.5000 0.8660 0.5000 1.7321 1.0000
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
hex=unique(hex,'rows');
given=[1.2,-1];
pts=[given;hex];
DT=delaunayTriangulation(pts);
CL=DT.ConnectivityList;
idx=any(CL==1,2);
idx=setdiff(CL(idx,:),1);
nearest=pts(idx,:)
nearest = 3x2
0 -1.0000 0.8660 -0.5000 1.7321 -1.0000
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
plot(hex(:,1),hex(:,2),'x', nearest(:,1),nearest(:,2),'o',given(:,1),given(:,2),'s');
legend Vertices Nearest Given
axis equal padded

Más respuestas (1)

Mario Malic
Mario Malic el 10 de Ag. de 2024
Hi,
here's some code to give you an idea
X = rand(3,3);
Y = rand(3,3);
pts = [X(:), Y(:)];
distance = squareform(pdist(pts)); % symmetric matrix that contains distances between points
% distance between pt3 and all other pts
[~, idx] = sort(distance(:, 3));
closestPts = idx(2:5) % first one is distance between pt3 and pt3 so we ignore that
  2 comentarios
Aravind Varma Dantuluri
Aravind Varma Dantuluri el 12 de Ag. de 2024
Thanks for the answer but this doesn't work.
  1. Not all points are not random. Only 1 is. The rest are vertices of hexagon.
  2. Sorting by distance won't work. Take the below example where the random point is blue mark:
We need to get the 4 points marked by the red line. But if we sort by distance, we omit the black mark and get the red mark.
Mario Malic
Mario Malic el 12 de Ag. de 2024
That random point is just an example, it can be arbitrary!

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