Counting occurences of each number in a column when it's equal to all numbers in the same line?

Question

João Cabral Pinto 2019-10-20

0
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https://ww2.mathworks.cn/matlabcentral/answers/486414-counting-occurences-of-each-number-in-a-column-when-it-s-equal-to-all-numbers-in-the-same-line

回答： Image Analyst 2019-10-20

I have, for example, the following matrix P:

How can I count the occurences of each number in the first column, only when it's equal to all numbers in the same line? For this example, the result would be:

I've tried something like this:

alpha = unique(P);
O = zeros(size(alpha));
for k = 1 : length(alpha)
    O(k) = sum(P(:,1) == alpha(k));
end

which counts the occurences for the first column of P, but I don't know how to exclude the cases where the line isn't all the same number. How should I alter my code?

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Answer 1

KALYAN ACHARJYA 2019-10-20

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在 MATLAB Online 中打开

P=[1 2 3
2 2 2
3 3 3
4 4 1
4 4 4
2 2 2
1 4 2];
[r c]=size(P);
for i=1:r
    if range(P(i,:))==0
    data=ismember(P,P(i,:),'rows');
    result(i)=sum(data);
    else
    result(i)=0;
    end
end
result'

Result:

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Answer 2

Image Analyst 2019-10-20

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https://ww2.mathworks.cn/matlabcentral/answers/486414-counting-occurences-of-each-number-in-a-column-when-it-s-equal-to-all-numbers-in-the-same-line#answer_397325

在 MATLAB Online 中打开

Try this:

P=[1 2 3
2 2 2
3 3 3
4 4 1
4 4 4
2 2 2
1 4 2];
allTheSame = P(:, 1) == P(:, 2) & P(:, 1) == P(:, 3) % Rows where all 3 values are the same.
counts = histcounts(P(allTheSame, 1), 1:max(P)+1)