Counting the number of the unique value in each row of a matrix without using for loop

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reza aghaee 2021-1-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/731313-counting-the-number-of-the-unique-value-in-each-row-of-a-matrix-without-using-for-loop

评论： Stephen23 2021-1-31

M = randi(21,[1000000,9]);
counter = zeros(size(A,1),1);
for j = 1 : size(A,1)    
    a = unique(Mat(j,:));
    counter(j) = numel(a);    
end

Hi

I have big size matrix (M in the above code) and I want to count the number of the unique value in each row.

I do not need the values and only the number of unique value is important to me.

The above for loop is a part of my program that needs to be repeated more and more times.

Because of the size of M, it is very time consuming and i dont want to use the above for loop.

Is there a faster alternative?

Thanks

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Iuliu Ardelean 2021-1-30

编辑：Iuliu Ardelean 2021-1-30

https://stackoverflow.com/questions/36970733/how-to-find-number-of-unique-elements-in-each-row-of-a-matrix

Your solution takes 10.6 seconds for me. One of the solutions in link above took 0.44 seconds.

Stephen23 2021-1-30

The reason why I gave up on Stack Exchange was because of too much incorrect information or very poor understanding of how to use MATLAB effectively. This thread is a good example, when the most popular answer starts with the remarkably narrow-minded "You need to use unique function on each row...".

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Answer 1

Stephen23 2021-1-30

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/731313-counting-the-number-of-the-unique-value-in-each-row-of-a-matrix-without-using-for-loop#answer_610288

在 MATLAB Online 中打开

M = randi(9,5,7)
M = 5×7
     5     4     8     4     9     6     9
     3     2     5     9     8     1     8
     4     4     8     7     3     3     1
     6     7     4     6     6     3     1
     6     3     4     2     5     9     7
N = 1+sum(diff(sort(M,2),1,2)~=0,2)
N = 5×1
     5
     6
     5
     5
     7

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reza aghaee 2021-1-30

Very cleverly

Thanke you so much

Stephen23 2021-1-31

@reza aghaee: please remember to accept my answer if it helped you!

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Counting the number of the unique value in each row of a matrix without using for loop

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