How to sort minimum value from a matrix

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Shin
Shin 2023 年 1 月 16 日
コメント済み: Shin 2023 年 1 月 16 日
Hi there, I have 2 set of array such as
number = 6;
A = 1+10*(rand(number,2));
B = [4,8; 6,8; 8,8; 6,6.7; 6,5.4; 6,4.1];
% Calculate all distance between set A and B for each elements
s = size(A);
dist = cell(1,s(1));
for idx = 1:s(1)
dist{idx} = vecnorm(B - A(idx,:),2,2);
end
dist = cell2mat(dist);
[minDist,index] = min(dist(:,:)); % obtain min distance and their index
The first set A is generated randomly and the second set B is fixed, and after running the code it will give a list of results such as
each column represent the distance from each element from set A to all in the set B. And the index indicate in which row the minium value located at. Hence, I was wondering how can sort the minimun value out, given that there might be huge posiballity of one of the point have the same minimun distance point as the figure show for index. If than happen, I would like to find the second minimum value to be the minimin value to ensure it wont obtain the same index of minimun value. For example, the index I would like to have the number 1 to 6 for each column and not repeated. Thanks.
-Chann-
  1 件のコメント
KSSV
KSSV 2023 年 1 月 16 日
Read about knnsearch

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採用された回答

Bruno Luong
Bruno Luong 2023 年 1 月 16 日
See matchpairs function
number = 6;
A = 1+10*(rand(number,2));
B = [4,8; 6,8; 8,8; 6,6.7; 6,5.4; 6,4.1];
% Calculate all distance between set A and B for each elements
s = size(A);
dist = cell(1,s(1));
for idx = 1:s(1)
dist{idx} = vecnorm(B - A(idx,:),2,2);
end
dist = cell2mat(dist)
dist = 6×6
2.0023 3.2585 6.6591 5.7172 5.5799 6.7287 1.3561 4.7442 5.4880 4.0241 4.9902 4.8789 2.7693 6.5113 4.8880 2.7749 5.1642 3.2142 2.6169 5.5625 4.3797 4.9478 3.7012 4.4545 3.9035 6.5387 3.4096 6.0123 2.4240 4.3889 5.1968 7.6124 2.7294 7.1551 1.1970 4.6970
M = matchpairs(dist,max(dist,[],'all'));
for k=1:size(M,1)
fprintf('Column %d matches row %d, dist(i,j) = %f\n', M(k,2), M(k,1), dist(M(k,1),M(k,2)))
end
Column 1 matches row 2, dist(i,j) = 1.356077 Column 2 matches row 1, dist(i,j) = 3.258484 Column 3 matches row 5, dist(i,j) = 3.409639 Column 4 matches row 3, dist(i,j) = 2.774933 Column 5 matches row 6, dist(i,j) = 1.196998 Column 6 matches row 4, dist(i,j) = 4.454540
  1 件のコメント
Shin
Shin 2023 年 1 月 16 日
Hi Bruno, thank you very much!! appreciate the help.

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その他の回答 (2 件)

KSSV
KSSV 2023 年 1 月 16 日
number = 6;
A = 1+10*(rand(number,2));
B = [4,8; 6,8; 8,8; 6,6.7; 6,5.4; 6,4.1];
idx = knnsearch(A,B)
idx = 6×1
6 2 4 2 3 3
  1 件のコメント
Shin
Shin 2023 年 1 月 16 日
Hi KSSV, thanks for your reply, however this method makes not different, the index will still appear to be repeating.

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Image Analyst
Image Analyst 2023 年 1 月 16 日
Try this:
number = 6;
A = 1+10*(rand(number,2))
B = [4,8; 6,8; 8,8; 6,6.7; 6,5.4; 6,4.1]
distances = pdist2(A, B)
% Find unique distances because it's possible some may be repeated.
udistances = unique(distances) % It's also sorted from in to max
% Find row and column for all the distances, from shortest to longest in sorted order.
for k = 1 : numel(udistances)
thisDistance = udistances(k);
fprintf('Min distance of %f at\n', thisDistance);
[indexA, indexB] = find(distances == thisDistance) % It's possible there will be multiple indexes if using integer coordinates.
end
  1 件のコメント
Shin
Shin 2023 年 1 月 16 日
Hi there, thanks for your solution.

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