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matlabmaxmatrix-indexing
Yuseferi
Yuseferi

Reputation: 8670

How can I find the maximum value and its index in array in MATLAB?

Suppose I have an array, a = [2 5 4 7]. What is the function returning the maximum value and its index?

For example, in my case that function should return 7 as the maximum value and 4 as the index.

Upvotes: 45

Views: 242513

Answers (7)

Pobaranchuk
Pobaranchuk

Reputation: 877

For example:

max_a = max(a)
a.index(max_a)

Upvotes: 0

oumarkh
oumarkh

Reputation: 11

This will return the maximum value in a matrix

max(M1(:))

This will return the row and the column of that value

[x,y]=ind2sub(size(M1),max(M1(:)))

For minimum just swap the word max with min and that's all.

Upvotes: 0

user3804598
user3804598

Reputation: 415

3D case

Modifying Mohsen's answer for 3D array:

[M,I] = max (A(:));
[ind1, ind2, ind3] = ind2sub(size(A),I)

Upvotes: 5

bonCodigo
bonCodigo

Reputation: 14361

You can use max() to get the max value. The max function can also return the index of the maximum value in the vector. To get this, assign the result of the call to max to a two element vector instead of just a single variable.

e.g. z is your array, 

>> [x, y] = max(z)

x =

7

y =

4

Here, 7 is the largest number at the 4th position(index).

Upvotes: 5

Rupal Sonawane
Rupal Sonawane

Reputation: 119

In case of a 2D array (matrix), you can use:

[val, idx] = max(A, [], 2);

The idx part will contain the column number of containing the max element of each row.

Upvotes: 10

Acorbe
Acorbe

Reputation: 8391

The function is max. To obtain the first maximum value you should do

[val, idx] = max(a);

val is the maximum value and idx is its index.

Upvotes: 85

Mohsen
Mohsen

Reputation: 314

For a matrix you can use this:

[M,I] = max(A(:))

I is the index of A(:) containing the largest element.

Now, use the ind2sub function to extract the row and column indices of A corresponding to the largest element.

[I_row, I_col] = ind2sub(size(A),I)

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

Upvotes: 16

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