Extracting name of variables from cell array

Question

Stephen 2016-4-27

0
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https://ww2.mathworks.cn/matlabcentral/answers/281350-extracting-name-of-variables-from-cell-array

回答： Kevin 2016-4-27

采纳的回答： Kevin

在 MATLAB Online 中打开

Dear All,

I have a cell array combin which contains all possible combinations of 4 elements ('A';'B';'C';'D') taken 3 at a time.

combin = 
      'A'    'B'    'C'
      'A'    'B'    'D'
      'A'    'C'    'D'
      'B'    'C'    'D'
coef = ['A';'B';'C';'D'];
coef = cellstr(coef);
combin = nchoosek(coef,3)

Each letter is also the variable name of a random number vector:

A = rand(10,1); B = rand(10,1); C = rand(10,1); D = rand(10,1);

I would like to obtain a matrix made of vectors A,B,C or D for each row of combin. For instance,

mod1 = [A B C];
...
mod4 = [B C D];

Any help would be highly appreciated.

Best, S.

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Answer 1

Kevin 2016-4-27

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https://ww2.mathworks.cn/matlabcentral/answers/281350-extracting-name-of-variables-from-cell-array#answer_219703

在 MATLAB Online 中打开

It will be much easier if we can turn your 'A', 'B', 'C', 'D' into 1, 2, 3, 4. For example,

>> coef = [1;2;3;4];
>> combin = nchoosek(coef, 3)
combin =
       1     2     3
       1     2     4
       1     3     4
       2     3     4

Also assume that we can put vectors {A, B, C, D} into one big matrix (say R). For example,

>> R = rand(10,4)
R =
8147    0.1576    0.6557    0.7060
9058    0.9706    0.0357    0.0318
1270    0.9572    0.8491    0.2769
9134    0.4854    0.9340    0.0462
6324    0.8003    0.6787    0.0971
0975    0.1419    0.7577    0.8235
2785    0.4218    0.7431    0.6948
5469    0.9157    0.3922    0.3171
9575    0.7922    0.6555    0.9502
9649    0.9595    0.1712    0.0344

Then the following one line will create vector mod1,

>> mod1 = R(:, combin(1,:))
mod1 =
8147    0.1576    0.6557
9058    0.9706    0.0357
1270    0.9572    0.8491
9134    0.4854    0.9340
6324    0.8003    0.6787
0975    0.1419    0.7577
2785    0.4218    0.7431
5469    0.9157    0.3922
9575    0.7922    0.6555
9649    0.9595    0.1712