How to insert a n x m matrix or table, into an existing table?

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Jens Allaert 2018-12-10

1
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评论： Peter Perkins 2018-12-11

Hello,

I would like to nest an n x m matrix into a table, by using a for loop to populate each row of the table with a corresponding matrix. I am running matlab 2018a. Below you can find example code:

% create the table
subject = [1; 2; 3; 4];
condition = {'cond1';'cond2';'cond3';'cond4'};
data = NaN(4,1);
T = table(subject,condition,data);
% populate the table with matrixes, using a for loop
for i = 1:1:size(T,1)
    data = rand(10,5);
    T.data(i) = data;    % ERROR Unable to perform assignment because the left and right sides have a different number of elements.
end    

I thought it was possible to create nested tables. However, I am not sure, on account of the error. I know tables within tables exists, but I am unsure whether you can nest a matrix/array in a table. Therefore, it is also allowed to transform the data matrix to a table, and then nest the table in the table. Of importance, I want to retain the for loop mechanism to populate the table.

Thanks in advance,

Jens

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Peter Perkins 2018-12-11

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Jens, it is definitely possible to put tables in tables, and (e.g. numeric) matrices in tables. There are two ways you might do that. The first is like this:

>> t = table(array2table(rand(5,2)),rand(5,2))
t =
  5×2 table
           Var1                  Var2       
     Var1       Var2                        
    __________________    __________________
    0.81472    0.09754    0.15761    0.14189
    0.90579     0.2785    0.97059    0.42176
    0.12699    0.54688    0.95717    0.91574
    0.91338    0.95751    0.48538    0.79221
    0.63236    0.96489    0.80028    0.95949

The second is like this:

>> t = table({array2table(rand(2));array2table(rand(3));array2table(rand(4))},{rand(5);rand(6);rand(7)})
t =
  3×2 table
       Var1            Var2    
    ___________    ____________
    [2×2 table]    [5×5 double]
    [3×3 table]    [6×6 double]
    [4×4 table]    [7×7 double]

These are two different storage schemes for two different kinds of data - in the first, each row of the inner table and matrix correspond to one row of the outer table, while in the second, each row of the outer table contains a table and a mtrix of different sizes. It sounds like you were looking for the second.

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