To find the maximum value in a matrix?

Let me have a 3X3 matrix

6   8   9
7   10  11
21  22  8

How to find the maximum value from this matrix?

[Jan]

Sorry that I mention the barely obvious, but the answer is 22.

[KHOIROM Motilal]

• clc
• close all
• clear all
• X=[99 67 65;
• 63 62 61;
• 41 40 9];
• MAX=X(1,1);
• for i=1:3
• for j=1:3
• if MAX<= X(i,j);
• MAX=X(i,j);
• end
• end
• end
• disp(MAX)

Answer 1

[Michael Völker]

Starting in R2018b, you can use the following command to find the maximum over all elements in an array A:

M = max(A, [], 'all');

For previous releases, use:

M = max(A(:));

[Image Analyst]

To get it's location as well, accept both outputs of max:

[maxValue, linearIndexesOfMaxes] = max(A(:));

Note that there can be the max value at more than one location. To get the rows and columns (instead of linear indexes), you can use ind2subs() or find():

[rowsOfMaxes colsOfMaxes] = find(A == maxValue);

Answer 2

[Azzi Abdelmalek]

 max(max(A))

[Andrei Bobrov]

M = [6   8   9
7   10  11
21  22  8];

index = 1;
max1 = M(index);
for jj = 2:numel(M)
    if max1 < M(jj)
        max1 = M(jj);
        index = jj;
    end
end

:)

[José-Luis]

Or if you really want to throw efficiency out the window:

M = [6   8   9
7   10  11
21  22  8];
unikM = unique(M);
val = unikM(1);
idx = unikM > val;
while (sum(idx) > 1)
    idx = find(idx);
    val = unikM(idx(1));
    idx = unikM > val;
    maxVal = unikM(idx)
end

[Jonathan Posada]

This works for the 2D case but if ndims(A)>2, then max(max(A)) will return a matrix. I believe OP wants the maximum element along all dimensions

Answer 3

[Tom]

M = max(A,[],'all') finds the maximum over all elements of A. This syntax is valid for MATLAB® versions R2018b and later.

[John Doe]

This should be upvoted and/or somehow appear closer to the chosen answer, as M = max(A,'all') seems not to work at all in R2018b+ (returning the entire matrix).

M = max(A(:)) seems to work in R2018b+ and presumably universally.

[Steven Lord]

The [] as the second input is required when you want to specify a dimension, including 'all'. The function call max(A, 'all') only works if A and 'all' are compatibly sized.

>> max(1:3, 'all')
ans =
    97   108   108
    
>> max(1:3, [], 'all')
ans =
     3    

Answer 4

[Dmaldo01]

This will work for all dimensions. If more efficient than ind2sub for less than 16000 elements.

 [M,Index] = maxEl(MatVar)

index = size(MatVar);
Index = index*0;
M = max(MatVar(:));

A = find(MatVar==max(MatVar(:)),1);
for i = 1:length(index)
   Index(i) = mod(ceil(A),index(i));
   A = A/index(i);
end
 Index(Index==0)=index(Index==0);

Answer 5

[Yokesh]

If matrix dimension is 'n', then max element can be found by:

max(max(.....maxn^2((A))...)

We have to include n^2 times max

[Steven Lord]

No, you don't need to include multiple calls to max. See the accepted Answer for approaches that call max only once regardless of how many dimensions the input argument has.

[Walter Roberson]

Also it would only be n max calls.