MATLAB Answers

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

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Anna M
Anna M on 24 Jun 2019
Commented: Anna M on 2 Jul 2019
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 Comments

Stephen Cobeldick
Stephen Cobeldick on 25 Jun 2019
"...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:
You should use indexing. Inexing is neat, easy to debug, and very efficient.

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Accepted Answer

James Tursa
James Tursa on 24 Jun 2019
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.,

  2 Comments

infinity
infinity on 25 Jun 2019
Hello, Thank @James Tursa for mentioning this issuse of eval function.
I recommend @Anna M to refer these solutions.

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More Answers (1)

infinity
infinity on 24 Jun 2019
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.