How do I add a known vector to an existing matrix in a loop?

I have 14 vectors from x1 to x14. I want to creat a loop that allows me to add a known vector to the previously created matrix, for example:

I have the matrix: in= [x1; x2; x3; x4; x5]

Now I want to create a loop that adds the other vectors to the matrix in. What I wrongly did was this:

for j=6:13

ta= xj; inj=[in; xj];

How do I put de x6, x7, x8 and so on into the matrix in6, in7, in8 and so on? My problema is getting the vectors by their names to work with them... The ta is a vector that I'll need in the problem.

[Guillaume]

The answer is not to create these numbered variables in the first place. As a rule, if you start numbering variables, you're doing something very wrong.

Much better is to put these variables in a cell array or as rows of a matrix (as you're trying to do now). It is then trivial to iterate over the vectors.

So rather than telling you how to fix the problem, it would be much better for us to tell you how not to create the problem in the first place. How did you create the variables?

[Jorge Gonçalves]

These variables, x1 to x14 are vectors of wind power values sent to me. So you're saying that the solution may be creating a matrix M that countains all the 14 vectors and then adding row by row to new matrix?

[Stephen23]

The core question is "how are these variables generated?"

If they are loaded from file data then they can be easily loaded into one variable. If they are hardcoded then change the code.

Answer 1

[James Tursa]

There is a way to do this using the eval function, BUT you are strongly advised against this approach. Rather, you should be using cell arrays or nD matrices for this. E.g., use x{1}, x{2}, etc instead of x1, x2, etc. That way you can get at them easily in a loop as you need. E.g., see this link:

http://www.mathworks.com/matlabcentral/answers/143-how-do-i-make-a-series-of-variables-a1-a2-a3-a10

[James Tursa]

If you have been sent these variables x1, x2, etc by someone else, then please advise them to modify their code! In the meantime, you can do this up front to put them into a manageable cell array that can be easily indexed in a loop:

n = number of variables
x = cell(n,1);
for k=1:n
    x{k} = eval(['x' num2str(k)]);
end

Answer 2

[Stephen23]

https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

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