For loop to extract every 3rd column out of matrix and assign as variable name

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Anna M
Anna M 2019-6-24
评论： Anna M 2019-7-2
I have a matrix that is 6001 x 72. I want to iterate through the matrix to extract every 3rd column, from 1:72, and assign it to a variable name, such as X1, X2,...,X24. How can I do this?
I have tried a for loop, but I keep getting error messages. I am a beginner in Matlab.
Thanks!
  2 个评论
Stephen23
Stephen23 2019-6-25
编辑：Stephen23 2019-6-25
"...assign it to a variable name, such as X1, X2,...,X24. How can I do this?"
Do NOT do this.
Accessing variable names is one way that beginners force themselves into writing slow, complex, buggy code that is hard to debug. Read these to know why:
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
You should use indexing. Inexing is neat, easy to debug, and very efficient.

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采纳的回答

James Tursa
James Tursa 2019-6-24
Do not do this! This will only lead to headaches downstream in your code for processing these variables (you will need to use more eval( ) statements etc) and will be a nightmare to debug. There are much better alternatives. E.g.,
https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

更多回答（1 个）

infinity
infinity 2019-6-24
Hello,
Here is an example that you can refer
for i = 1:24
v = genvarname(['X' num2str(i)]);
eval([v '= A(:,3*i);']);
end
where A is your matrix.

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