Matrix manipulation: update columns from stored variables

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ARP 2017-3-17

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https://ww2.mathworks.cn/matlabcentral/answers/330323-matrix-manipulation-update-columns-from-stored-variables

评论： Star Strider 2017-3-17

Suppose I have a set of variables (15) as column vectors, called A from 1-15. Now I would like to make a matrix of all those variables. They have 12501 rows if that helps.

I thought about creating first a zeros matrix (12501,15), and then append each column with my variables.

is there other way to do it? I read about cell2mat but I don't get it. I am truly beginner..

How could I do it in a loop for n variables?

Any help will be very appreciated! Thanks

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Answer 1

Star Strider 2017-3-17

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‘I have a set of variables (15) as column vectors, called A from 1-15’

If they are ‘A1’, ‘A2’, ... ‘A15’, and you only need to do this once, just type it manually:

A_Matrix = [A1 A2 A3 A4 A5 ... A15];

I will let you fill in the others.

Then save it as a ‘.mat’ file so you can simply load it when you need it.

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ARP 2017-3-17

How do I tell to Matlab to count how many variables do I have?

Star Strider 2017-3-17

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I was thinking that if you only had 15 vectors, you could just type them in.

If you want to program it, this will probably work:

N = 15;                                        % Number Of ‘A’ Vectors
A_Matrix = zeros(12501,N);
for k1 = 1:N
    A_Matrix(:,k1) = eval(sprintf('A%d',k1));
end