Dynamically assign structure names and loop them in fuction

Hello

I am trying to dynamically assign some of my variable names which are structures and them pass them through a script although I get an error

DATA=who('DATA*')
ORIG=who('ORIGINAL*')

countS=length(DATA)
countC=length(ORIG)
if countS==countC;
    for i=1:countS
figure
    scatter(DATA{i,1}.H,ORIGINAL{i,1}.H)
lm(i)=polyval(DATA{i,1}.H,ORIGINAL{i,1}.H)
    end      
end

Though i get Attempt to reference field of non-structure array. The structures themselves contain fields that i want to iterate through other processes, am I doing something wrong?

thanks

[Stephen23]

Do not use dynamically names variables in MATLAB. Put your variables in a cell array instead.

The answers will explain why, and please understand them if you want to write good code.

This is the third time that you have asked a question that used dynamically named variables and faced a difficult problem because of that choice: each time the advice given was "do not use dynamically named variables", and reasons were given.

http://de.mathworks.com/matlabcentral/answers/90381-concatenate-mutiple-tables-repetative

http://de.mathworks.com/matlabcentral/answers/90359-concatenate-mutiple-tables-by-repetative-process

Answer 1

[Stephen23]

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

[George]

I am using structures, the names are created by the structures loaded in a previous load sequence/generation. The structures themselves have inside them various data.I only use the dynamic naming so as to automate the loading.clearing processing process

[Stephen23]

Every time you use dynamically named variables you write a question here: "why is this difficult?", and the advice is "don't do this". Three times with the same problem and three times the same answer.

Answer 2

[James Tursa]

The result of the who command simply gives you variable names as a cell array of strings ... it doesn't give you the variables themselves. Thus, DATA{i,1} is a string that is the name of a variable ... it is not the variable itself so you can't use .H syntax to get at the H field. You will probably need to use something like eval to get at the variable. E.g.,

scatter(eval([DATA{i,1} '.H']),eval([ORIGINAL{i,1} '.H']))

lm(i) = polyval(eval(DATA{i,1} '.H']),eval([ORIGINAL{i,1} '.H']));

This is admittedly ugly, but that is typically what you end up with when you have a multitude of variables in your workspace with similar names that you need to loop over. A better practice is often to have such variables gathered up into a single cell array instead. This makes accessing them in a loop much easier, and allows the use of MATLAB functions that operate on cell arrays (often avoiding loops altogether). E.g.,

http://www.mathworks.com/matlabcentral/answers/57445-faq-how-can-i-create-variables-a1-a2-a10-in-a-loop