How do I find the indices of the maximum (or minimum) value of my matrix?

The 'find' command only returns the indices of all the non-zero elements of a matrix. I would like to know how to find the indices of just the maximum (or minimum) value.

Answer 1

[MathWorks Support Team]

The "min" and "max" functions in MATLAB return the index of the minimum and maximum values, respectively, as an optional second output argument.

For example, the following code produces a row vector 'M' that contains the maximum value of each column of 'A', which is 3 for the first column and 4 for the second column. Additionally, 'I' is a row vector containing the row positions of 3 and 4, which are 2 and 2, since the maximums for both columns lie in the second row.

A = [1 2; 3 4];
[M,I] = max(A)

For more information on the 'min' and 'max' functions, see the documentation pages listed below:

https://www.mathworks.com/help/matlab/ref/double.max.html

https://in.mathworks.com/help/matlab/ref/min.html

To find the indices of all the locations where the maximum value (of the whole matrix) appears, you can use the "find" function.

https://www.mathworks.com/help/matlab/ref/find.html

maximum = max(max(A));
[x,y]=find(A==maximum)

Answer 2

[Shakir Kapra]

[M,I] = min(A) 
where M - is the min value
and I - is index of the minimum value
Similarly it works for the max

Answer 3

[indrajit das]

find(arr == max(arr));

Answer 4

[Andrew Teixeira]

How about just:

A = magic(5);    
[Amins, idx] = min(A);
[Amin, Aj] = min(Amins);
Ai = idx(Aj);

where your final matrix minima is located at [Ai, Aj]

Answer 5

[Juanith HL]

A = [8 2 4; 7 3 9]

[M,I] = max(A(:)) %I is the index maximun Here tu can change the function to max or min

[I_row, I_col] = ind2sub(size(A),I) %I_row is the row index and I_col is the column index

[Steven Lord]

If you can use linear indices, instead I would recommend:

A = [8 2 4; 7 3 9];
[X, ind] = max(A, [], 'all', 'linear')

X = 9

ind = 6

This will tell us the maximum value in A is 9 and it is located in element 6 of A.

Answer 6

[ANKUR KUMAR]

Use this as a function and type [x,y]=minmat(A) to get the location of the minimum of matrix. for example:

>> A=magic(5)
>> [a,b]=minmat(A)
a =
     1
b =
     3

Save this as a function in your base folder and use it.

function [ a,b ] = minmat( c )
as=size(c);
total_ele=numel(c);
[~,I]=min(c(:));
r=rem(I,as(1));
a=r;
b=((I-a)/as(1))+1;
if a==0
    a=as(1);
    b=b-1;
else
    a=r;
    b=b;
end
end

[Steven Lord]

Once you've stored this code in a file named minmat.m (see this documentation page for the basics of defining a function) you can call this like any other MATLAB function (as shown on this other documentation page.)