Concatenate variables with similar names

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Ricardo Duarte 2021-6-8

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https://ww2.mathworks.cn/matlabcentral/answers/850610-concatenate-variables-with-similar-names

编辑： Ricardo Duarte 2021-6-8

采纳的回答： Stephen23

Dear all

I need to concatenate several variables with similar name.

For example: T=cat(3,SPL_A,SPL_B,SPL_C,SPL_D,SPL_E).

This procedure is easy when you have just a few variables, as I show you in the previous line, however in my case I have hundreds of variables which makes almost impossible to do it by hand.

The variables have all the same starting name which I guess could help in the process, but Im not realizing how to do it.

Thanks in advance

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Ricardo Duarte 2021-6-8

Using a loop.

KSSV 2021-6-8

So you are creating the variables. You could concatenate them while generating those variables in a loop.

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Stephen23 2021-6-8

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编辑：Stephen23 2021-6-8

在 MATLAB Online 中打开

"Using a loop."

Then that is where you should fix the bad code design.

Meta-data is data, so store it in arrays, not in variable names.

Forcing meta-data (e.g. positions, frequencies) into variable names is one way that beginners force themselves into writing slow, inefficient, complex code that is liable to bugs and yet difficult to debug:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

"this procedure is easy when you have just a few variables"

It is also very easy when you have an arbitrary number of arrays. The simple and efficient solution is to keep your data in just a cell array, then you can use comma-separated lists to concatenate those arrays:

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

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

For example:

N = number of arrays.
C = cell(1,N); % preallocate!
for k = 1:N
    ... your code
    C{k} = whatever output array you want
end
M = cat(3,C{:}); % so simple.

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Ricardo Duarte 2021-6-8

Thank you, but this will only concatenate the names of the variables and I want to concatenate the content of each variable.

Ricardo Duarte 2021-6-8

编辑：Ricardo Duarte 2021-6-8

It works, thank you

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SALAH ALRABEEI 2021-6-8

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编辑：SALAH ALRABEEI 2021-6-8

在 MATLAB Online 中打开

@Ricardo Duarte Here is a trick, you will save all your workplace into one variable b; then loop over all of them to take whose variables who have the same size ( which are those you want to concatenate ). Assuming your variables that you need to concatenate are of size 20 x 30. However, if a any variable the same size as 20 x 30 will be concatenated

b = whos;
ConMat = [];
for i = 1:length(b)
if sum(b(i).size) == sum([20,30])
ConMat=[ConMat;eval(b(i).name)];
end
end

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SALAH ALRABEEI 2021-6-8

Thank you @Stephen Cobeldick, I have just check you invaluable complete Tech report in the importance of properly naming the varaibles. I didn't expect that until I read part of it.

Regarding to my comment, I was expecting a faster way to fix the issue of @Ricardo Duarte ( where there are several variables. Thank you though.