Working with cell arrays

Question

L'O.G. 2023-5-5

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1958654-working-with-cell-arrays

评论： Stephen23 2023-5-8

I would like to separate columns in an array based on the unique values of the first column. I think the way to do this is a cell array since the vectors would be of different length. Is there a way to vectorize this? For example, the following array

example = [

5 2.3 1.7

5 0.2 9.1

99 3.3 3.6

99 4.1 3.2

99 5.1 2.2

103 1.1 6.8

];

should give

A{1} = [2.3,0.2];

A{2} = [3.3,4.1,5.1];

A{3} = [1.1];

B{1} = [1.7,9.1];

B{2} = [3.6,3.2,2.2];

B{3} = [6.8];

(since there are three unique values in column 1 of the example)

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Answer 1

Paul 2023-5-5

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https://ww2.mathworks.cn/matlabcentral/answers/1958654-working-with-cell-arrays#answer_1229979

在 MATLAB Online 中打开

example = [
5 2.3 1.7
5 0.2 9.1
99 3.3 3.6
99 4.1 3.2
99 5.1 2.2
103 1.1 6.8
];
G = findgroups(example(:,1));
A = splitapply(@(x) mat2cell(x,numel(x)),example(:,2),G);
B = splitapply(@(x) mat2cell(x,numel(x)),example(:,3),G);
A,B
A = 3×1 cell array
    {2×1 double}
    {3×1 double}
    {[  1.1000]}
B = 3×1 cell array
    {2×1 double}
    {3×1 double}
    {[  6.8000]}
A{1}
ans = 2×1
    2.3000
    0.2000
B{1}
ans = 2×1
    1.7000
    9.1000

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Stephen23 2023-5-8

在 MATLAB Online 中打开

Also without the MAT2CELL call:

X = [
    5 2.3 1.7
    5 0.2 9.1
    99 3.3 3.6
    99 4.1 3.2
    99 5.1 2.2
    103 1.1 6.8
    ];
G = findgroups(X(:,1));
A = accumarray(G,X(:,2),[],@(a){a});
B = accumarray(G,X(:,3),[],@(a){a});
A,B
A = 3×1 cell array
    {2×1 double}
    {3×1 double}
    {[  1.1000]}
B = 3×1 cell array
    {2×1 double}
    {3×1 double}
    {[  6.8000]}
A{1}
ans = 2×1
    2.3000
    0.2000
B{1}
ans = 2×1
    1.7000
    9.1000