Count how many times a number is repeated in a certain row of an array

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Nathaniel Werner 2018-7-20

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评论： PEDRO ALEXANDRE Fernandes 2022-3-4

采纳的回答： Aquatris

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Please consider the array

A = [1;1;1;2;2;2;2;2;3;3;4;4;4;4;4;4;4;5;5;5;5];

I would like to determine how many times each number repeats.

For 1, it repeats three times. For 2, it repeats five times, and so on.

If there is other data in columns to the left of the array A that does not follow the same repeating pattern, can I still count how many times each number in a certain column is repeated?

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Adam 2018-7-20

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doc histcounts

would be one way of doing it, depending on how many unique values you are likely to have, though however many there are you could use that many bins.

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Aquatris 2018-7-20

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Here is a code;

 A = [1;1;1;2;2;2;2;2;3;3;4;4;4;4;4;4;4;5;5;5;5];
 c = unique(A); % the unique values in the A (1,2,3,4,5)    
 for i = 1:length(c)
   counts(i,1) = sum(A==c(i)); % number of times each unique value is repeated
 end
 % c(1) is repated count(1) times

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Aquatris 2020-5-5

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From the above example, the code can be (for relatively newer versions of Matlab;

d = c(counts<4);

where d has the value that appear less than 4 times in the A vector. Alternatively;

I = find(counts<4); % find indices where counts variable elements are less than 4
d=c(I);             

PEDRO ALEXANDRE Fernandes 2022-3-4

Hi. I have a similar problem. if i have a multidimensional array of the style 7 X 10

9 5 2 1 5 3 3

1 8 3 1 7 4 3

1 3 1 1 8 6 4

1 3 1 6 4 2 1

2 1 6 3 2 2 1

2 3 1 1 7 5 4

1 1 4 2 1 8 6

Columns 8 through 10

2 2 5

2 2 6

4 2 4

2 9 7

1 9 1

2 1 5

5 4 5

and I intend to count the number of times each digit appears per line.

Example: on line 1

1 -> 1

2 -> 3

3 -> 2

and then the same in the following lines. Any idea?

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