How to find the 5 minimum values in a multidimensional matrix and the indices to which these entries correspond.
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Charles Howman
on 23 Dec 2022
Edited: Charles Howman
on 23 Dec 2022
I have a 597 x 194 matrix to which I need to find the 5 smallest values within the entire matrix. As well as this I need the corresponding indices for those minimum values.
i.e. the smallest value (of the 5) is value 4.1146, and corresponds to indices of 336, 170. How could I find this value along with the next 4 smallest, and the indices for the entry?
2 Comments
Robin
on 23 Dec 2022
To find the 5 smallest values in a matrix and their corresponding indices, you can use the min function along with the sort and ind2sub functions in MATLAB. Here is an example of how to do this:
%
% Define the matrix
% (this is terrible, since you are likely to get multiple
% zeros as random values over the 115818 element matrix
A = rand(597, 194);
% Find the 5 smallest values and their indices
[sortedValues, sortedIndices] = sort(A(:));
smallestValues = sortedValues(1:5);
smallestIndices = sortedIndices(1:5);
% Convert the linear indices to row-column indices
[rowIndices, colIndices] = ind2sub(size(A), smallestIndices);
% Print the results
fprintf('Smallest value: %.4f, indices: (%d, %d)\n', ...
smallestValues(1), rowIndices(1), colIndices(1));
fprintf('Second smallest value: %.4f, indices: (%d, %d)\n', ...
smallestValues(2), rowIndices(2), colIndices(2));
fprintf('Third smallest value: %.4f, indices: (%d, %d)\n', ...
smallestValues(3), rowIndices(3), colIndices(3));
fprintf('Fourth smallest value: %.4f, indices: (%d, %d)\n', ...
smallestValues(4), rowIndices(4), colIndices(4));
fprintf('Fifth smallest value: %.4f, indices: (%d, %d)\n', ...
smallestValues(5), rowIndices(5), colIndices(5));
This code first flattens the matrix into a vector using the : operator and then sorts it using the sort function. It then selects the first 5 values and their indices and converts the linear indices to row-column indices using the ind2sub function. Finally, it prints the results to the command window.
I hope this helps! Let me know if you have any questions.
Accepted Answer
the cyclist
on 23 Dec 2022
% Some input data
rng default
M = rand(3);
% Find the sorted values of M, and the linear matrix indexing to them
[sortedM,linearIndex] = sort(M(:));
% Find the row and column indices
[rowIndex,columnIndex] = ind2sub(size(M),linearIndex);
% The first 5 of them
n = 5;
sortedM(1:n)
rowIndex(1:n)
columnIndex(1:n)
More Answers (1)
William Rose
on 23 Dec 2022
A=rand(3,4)
[r,c]=size(A);
k=5; %number of values to find
[minval,idx]=mink(reshape(A,[],1),k);
minrow=mod(idx,r);
minrow(minrow==0)=3;
mincol=ceil(idx/r);
disp([minval,minrow,mincol])
Try it. Good luck.
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