Number of counts in matrix

Question

Prince 2024-4-3，21:00

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评论： Voss 2024-4-3，22:07

How to count the number of individual elements in a matrix using matlab? I mean the number of times individual elements appear.

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Answer 1

Voss 2024-4-3，21:13

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在 MATLAB Online 中打开

You can use nnz.

Example:

A = [1 1 2; 2 1 2; 3 1 1]
A = 3x3
     1     1     2
     2     1     2
     3     1     1
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nnz(A == 1) % number of times 1 appears in A
ans = 5
nnz(A == 2) % number of times 2 appears in A
ans = 3
nnz(A == 3) % number of times 3 appears in A
ans = 1

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Voss 2024-4-3，21:42

在 MATLAB Online 中打开

You're welcome!

Here's one way to do it all at once:

A = randi([1,10],15,15)
A = 15x15
     6     8     9     5     1     1     1    10     6    10     1     2     6    10     4
     2     9     7     1     8     2     5     4     7     7     3    10     6     4     5
     3     5     9     6    10    10     9     9    10     2     1     6     4     6     3
     5     7     1     5     2     7     7     2     2     3     7     3     6    10     5
     2     4     2     6     9    10     8     7     1     6     3     3    10     1    10
     6     8     4     4     9     8     5     9     1     2     4     5     1     3     2
     1     3    10    10     4     6     1     6     4     8     3     7     2     3     1
    10     9    10     6     6     6     4    10     7     8     7     9     9     8     2
     1     3     2     8     6     5     2     6     9    10     6     9     5     8     2
     9     6     7     4     6     8     5     5     4    10     9     6     3     1     7
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[g,value] = findgroups(A(:));
count = groupsummary(A(:),g,'nnz');
result = table(value,count)
result = 10x2 table
    value    count
    _____    _____

      1       24  
      2       27  
      3       19  
      4       22  
      5       23  
      6       30  
      7       21  
      8       16  
      9       21  
     10       22  

Prince 2024-4-3，22:04

It worked. Thank you so much

Voss 2024-4-3，22:07

Great! You're welcome!

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Answer 2

Steven Lord 2024-4-3，21:32

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Use histcounts with unique (or uniquetol) to generate the bins. You will need to add one more bin at the end since the last bin includes both its edges (unlike the other bins, which only include their left edges.) I would use inf as the right-most end of that last bin.