Error in using eval statement

Why it shows an incomplete statement ?

I'm trying to write this statement using eval as follows : Energy_H_A1S1 = rms (H_A1S1); but in eval it shows error ?

Thanks in advance.

 eval(['Energy_H_A',num2str(1),'S',num2str(1),'  = rms(H_A',num2str(1),'S',num2str(1);]);

[Stephen23]

"I'm trying to write this statement using eval as follows : Energy_H_A1S1 = ..."

And that is the start of your problems.

Forcing meta-data into variable names makes acessing your data complex, slow, inefficient, and buggy... as your question demonstrates. Meta-data is data. Data should be stored in variables, not in variable names.

Your poor data design forces you into writing bad code, which could be easily avoided by storing the meta-data correctly.

[Ramesh Bala]

Thank you Stephen for your valuable reply.Yes that's right using names was wrong as it was indeed slow.

Answer 1

[Paul]

There's almost certainly a better way to organize the data and store the results, but if you must use eval:

['Energy_H_A',num2str(1),'S',num2str(1),'  = rms(H_A',num2str(1),'S',num2str(1);]

ans = 'Energy_H_A1S1  = rms(H_A1S1'

should be:

['Energy_H_A',num2str(1),'S',num2str(1),'  = rms(H_A',num2str(1),'S',num2str(1),');']

ans = 'Energy_H_A1S1  = rms(H_A1S1);'

[Ramesh Bala]

thank you for youe valuable answer

[Ramesh Bala]

Dear Paul,

Could you please also post an example of the mentioned better way instead of eval as it takes high running time for this varying A1..4..S1..4 data

for i =1:4 
eval (['Energy_H_A',num2str(1),'S',num2str(1),'  = rms(H_A',num2str(1),'S',num2str(1),');'])
end

[Paul]

Alternatives are dicussed in the link posted by @Walter Roberson in his comment.

[Stephen23]

"Could you please also post an example of the mentioned better way instead of eval as it takes high running time for this varying A1..4..S1..4 data"

The MATLAB introductory tutorials also show how to use MATLAB effectively by using arrays and indexing:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

Answer 2

[Walter Roberson]

Asking how to use eval without problems is like asking how to use a chainsaw without its chain guard. It would be irresponsible for us to answer in any way other than "Don't do that!"

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

[Ramesh Bala]

Thank you Walter ,Indeed Eval was causing slowness when runnign the code.Thank you for the link