Is there a way to append all arrays nested in a table without looping?

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Sam 2023-4-18

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评论： Stephen23 2023-9-12

Hello all,

I have a matlab table t with a column d of arrays as shown below. Is there a way to concatenate all the arrays in d to a new variable say D without looping through the array? I am avoiding looping because it is so slow.

Thanks and regards.

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Dyuman Joshi 2023-4-18

How do you want to concatenate them? Horizontally? Vertically? Or otherwise?

Stephen23 2023-9-12

在 MATLAB Online 中打开

The variable/column D must be a cell array inside that table, so you can simply use a comma-separated list:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

For example, where T is your table:

D = horzcat(T.d{:})
D = vertcat(T.d{:})

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Answer 1

Rik 2023-4-18

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Something like this should work:

t = table({19;17},{rand(100,1);rand(100,1)},'VariableNames',{'Umean','d'})
t = 2×2 table
    Umean           d       
    ______    ______________

    {[19]}    {100×1 double}
    {[17]}    {100×1 double}
D=cell2mat(t.d);
size(D),class(D)
ans = 1×2
   200     1
ans = 'double'

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Sam 2023-4-18

Thanks guys. Now I have column of timetable where I only need that data. Is there a similar simple way to go about it?

Thanks in advance

Rik 2023-4-18

在 MATLAB Online 中打开

Can you post example code that generates a similar variable? I showed you an example, and as you can see, that way it is easy to show you what to do.

I expect cell2mat complains, since you must have already tried it. You can also use vertcat:

tmp = t.i;
D = vertcat(tmp{:});

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Answer 2

KSSV 2023-4-18

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D = table2array(T.d)

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Stephen23 2023-4-18

编辑：Stephen23 2023-4-18

"T.d directly results in vertical concatenation if the data is numeric (which it looks like is the case in OP's data)"

To get 100x1 numeric data in one row requires nesting the numeric data inside a cell array. In the Workspace Viewer this is displayed without the curly braces, exactly as the OP's screenshot shows.

Your example creates 1x100 numeric vectors in each row, not 100x1 vectors like the OP.

Dyuman Joshi 2023-4-18

Stephen, I am aware that my example creates 1x100 numeric vectors, which is what I mentioned in my comment as well.

"In the Workspace Viewer this is displayed without the curly braces"

I overlooked this. I will delete my above comment.

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Is there a way to append all arrays nested in a table without looping?

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