Separate data series based on parameter within the data.

I have a data series 50704x4 which contains data that looks roughly like this

A = [1,n,n,n;
    1,n,n,n;
    2,n,n,n;
    ...
    100,n,n,n]

where the n are numerical data and the 1,2,...,100 are the frequency that i logged data for. I want to change this to have a distinct A1, A2, ... for each frequency.

If it is useful, the frequencies used are 1,2,3.3,5,8,10,20,40,50,70,90, and 100

how can i seperate these data?

[Stephen23]

https://www.mathworks.com/matlabcentral/discussions/tips/849901-tutorial-why-variables-should-not-be-named-dynamically-eval

Answer 1

[Stephen23]

A = [1,12,13,14; 1,21,23,24; 2,32,33,34; 100,42,43,44]

A = 4×4

1 12 13 14 1 21 23 24 2 32 33 34 100 42 43 44

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[G,ID] = findgroups(A(:,1));

Method one:

F = @(x)A(x==A(:,1),:);
C = arrayfun(F,ID,'uni',0)

C = 3x1 cell array
    {2x4 double    }
    {[  2 32 33 34]}
    {[100 42 43 44]}

C{:}

ans = 2×4

1 12 13 14 1 21 23 24

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ans = 1×4

2 32 33 34

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ans = 1×4

100 42 43 44

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Method two:

F = @(x)A(x==G,:);
C = arrayfun(F,1:max(G),'uni',0)

C = 1x3 cell array
    {2x4 double}    {[2 32 33 34]}    {[100 42 43 44]}

C{:}

ans = 2×4

1 12 13 14 1 21 23 24

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ans = 1×4

2 32 33 34

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ans = 1×4

100 42 43 44

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Method three:

F = @(x){A(x==A(:,1),:)};
V = 1:numel(ID);
C = accumarray(V(:),ID,[],F)

C = 3x1 cell array
    {2x4 double    }
    {[  2 32 33 34]}
    {[100 42 43 44]}

C{:}

ans = 2×4

1 12 13 14 1 21 23 24

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ans = 1×4

2 32 33 34

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ans = 1×4

100 42 43 44

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Method four:

F = @(x){A(x,:)};
V = 1:size(A,1);
C = splitapply(F,V(:),G)

C = 3x1 cell array
    {2x4 double    }
    {[  2 32 33 34]}
    {[100 42 43 44]}

C{:}

ans = 2×4

1 12 13 14 1 21 23 24

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ans = 1×4

2 32 33 34

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ans = 1×4

100 42 43 44

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See: https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html

"how can i seperate these data?"

Note that splitting up data like that is often not required (and is in many cases an inefficient approach to data storage/processing):

https://www.mathworks.com/help/matlab/matlab_prog/perform-calculations-by-group-in-table.html