how to separate a matrix according to class labels?

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Ararat Cetinkaya 2020-3-7

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https://ww2.mathworks.cn/matlabcentral/answers/509548-how-to-separate-a-matrix-according-to-class-labels

回答： Guillaume 2020-3-7

Hi everybody,

I have a matrix with size of 1500x3. Third column of the this matrix contains the class labes as a numeric like 3,2,1 and size of the each classes is uncertain. I want to divide the main matrix into three different matrices according to these three different classes. Only elements from class 1 will be taken in the first matrix, Only elements from class 2 will be taken in the second matrix, Only elements from class 3 will be taken in the third matrix.

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Answer 1

Guillaume 2020-3-7

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https://ww2.mathworks.cn/matlabcentral/answers/509548-how-to-separate-a-matrix-according-to-class-labels#answer_418996

在 MATLAB Online 中打开

classmatrices = splitapply(@(rows) {yourmatrix(rows, :)}, (1:size(yourmatrix, 1)'), yourmatrix(:, 3))

is one way. Note that in matlab it's rarely useful to do this splitting. It's often easier to work on the whole 1500x3 matrix and use aggregation functions such as groupsummary.