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Concatenate variables with similar names

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Ricardo Duarte
Ricardo Duarte el 8 de Jun. de 2021
Editada: Ricardo Duarte el 8 de Jun. de 2021
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
  9 comentarios
Ricardo Duarte
Ricardo Duarte el 8 de Jun. de 2021
Using a loop.
KSSV
KSSV el 8 de Jun. de 2021
So you are creating the variables. You could concatenate them while generating those variables in a loop.

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Stephen23
Stephen23 el 8 de Jun. de 2021
Editada: Stephen23 el 8 de Jun. de 2021
"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:
"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:
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.
  2 comentarios
Ricardo Duarte
Ricardo Duarte el 8 de Jun. de 2021
Thank you, but this will only concatenate the names of the variables and I want to concatenate the content of each variable.
Ricardo Duarte
Ricardo Duarte el 8 de Jun. de 2021
Editada: Ricardo Duarte el 8 de Jun. de 2021
It works, thank you

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Más respuestas (1)

SALAH ALRABEEI
SALAH ALRABEEI el 8 de Jun. de 2021
Editada: SALAH ALRABEEI el 8 de Jun. de 2021
@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
  6 comentarios
SALAH ALRABEEI
SALAH ALRABEEI el 8 de Jun. de 2021
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.
Stephen23
Stephen23 el 8 de Jun. de 2021
Editada: Stephen23 el 8 de Jun. de 2021
"It would be great if there were a function that does so easily"
The comma-separated list syntax efficiently concatenates arbitrary numbers of arrays together.

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