How to loop through a set of variables Y1..Y100

Hi,

I've a group of matrix named Y1 .. Y100. Each matrix is 7244x1 (complex number).

I want to loop through them (Y1..Y100) so in each iteration I can plot the 7244x1 values.

How can I iterate through them?

Thanks in advance

[James Tursa]

Don't create these variables in the first place.

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

[Ahmed AKL]

Actually I didn't create them. This is the way my spectrum analyser exports the data to Matlab

[James Tursa]

Ugh ...

[Stephen23]

"This is the way my spectrum analyser exports the data to Matlab"

But you still have to import that data somehow into the MATLAB workspace, and there is no reason why it has to be imported as lots of separate variables. For example load can easily be used with an output variable, which thus removes the need to use slow, complex, buggy eval. If you told us how you are getting this data into your workspace then we could show you better ways of doing this.

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

[Ahmed AKL]

Sure, it will be nice if you can find a way to import the data in a better format.

The analyzer captures the RF signal and exports it to a .mat file (it doesn't give me any option to configure the format). Then I go to Matlab and load the .mat file, so I've a punch of data in my workspace as I explained in the question.

Do you have a solution for this?

[Stephen23]

"Do you have a solution for this?"

Yes, as I already wrote, just load the data into a variable. This was also explained in the tutorial that I gave you a link to: did you read it? See my answer for how this can be applied to your situation.

Answer 1

[Stephen23]

"it will be nice if you can find a way to import the data in a better format."

Of course, it is simpler and more efficient to load into an output a structure and then access its fieldnames:

figure()
hold on
S = load(...);
For k = 1:100
    plot(real(S.(sprintf('Y%d',k))))
end

So easy! By simply avoiding eval I wrote more efficient code using fewer characters: when beginners learn to avoid eval then they also write simpler, less buggy, more efficient code:

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

Answer 2

[jonas]

Try this:

figure;hold on

    for i=1:100;
    plot(eval(sprintf(['Y',num2str(i)])));
    end

For more info: https://se.mathworks.com/matlabcentral/answers/57445-faq-how-can-i-create-variables-a1-a2-a10-in-a-loop

EDIT: For future reference, Stephen gave a better solution below. Only use EVAL() if it is absolutely necessary (which it rarely is, if ever?). See link for more info.

[Ahmed AKL]

Thanks a lot.

It works fine. but I made a small change to plot the real value without the imaginary part

plot(real ( eval(sprintf(['Y',num2str(i)]))) );

[Stephen23]

Even better would be to import the data properly so that slow and buggy eval is not required.

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