How to calculate repetition of an unknown number present in 2nd column of a 150*2 matrix?

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Binayak Gouda
Binayak Gouda 2016년 5월 20일
댓글: Star Strider 2016년 5월 21일
I've a matrix a=[1,1;2,1;3,1;4,4;5,4] . Actually numbers in the 2nd column are not known in a general case. So, how can i count how many numbers have a particular number (say 1,4) in their corresponding 2nd column.

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Star Strider
Star Strider 2016년 5월 20일
Use the unique and accumarray functions:
a=[1,1;2,1;3,1;4,4;5,4];
[a2,ia,ic] = unique(a(:,2));
ah = accumarray(ic, 1);
Result = [a2, ah]
Result =
1 3
4 2
So in the second column, there are 3 ‘1’ values and 2 ‘4’ values.
This could be easily changed if you wanted unique row pairs.

추가 답변 (1개)

Alessandro Masullo
Alessandro Masullo 2016년 5월 20일
You can use the function hist (or histc) on the second column of your matrix.

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