How to Rename all variables

hello,

If a certain if statement is true, i want to rename alle the variables that contains "MAIN_" to "New Name". (All vectors)

Is there an easy way to do this? I tried the rename function but that does not work with double's.

Answer 1

[Guillaume]

A variable can't be renamed. All you can do is create a copy of the old one with a new name and then clear the old one:

NewName = Main;
clear Main;

Due to the way matlab works, there won't be any copy actually.

However, there shouldn't be any reason for you to want to rename variables in the first place. If you do, it's most likely because you've been using dynamic variable names, which is a bad idea in the first place

Answer 2

[Stephen23]

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

[Nick van der maat]

I am expecting to get a vector 1.000.000 x 1. Out of this i will determine different trips. So i will create an new variable ....Trip1 = part of the vector. And create for al variables new ones .....Trip1 = containing the same part of the vector.

Then i use another if statement over this trip1 and rename all trip1variables to Trip1_Urban_Mass1.

[Guillaume]

This is exactly the kind of scenario we're warning you against. Store your trips into a cell array or a structure array (and with structures, I'd stay clear of dynamic field names as well).

It will make your life much easier in the long run, starting with not having to rename anything. For example, using a structure array:

Trips = struct('name', '', 'route', []); %predeclare structure, would be even better if size is known in advance
tripcount = 0;
while ... %loop that calculate trip
   %... calculate trip
   tripcount = tripcount + 1;
   Trip(tripcount).name = sprintf('Trip%d_Urban_Mass%d', tripcount, someothernumber);
   Trip(tripcount).route = rand(10); 
end

[Stephen23]

@Nick van der maat: yes, we know what you are trying to do and that is exactly what we are giving advice about. It is considered to be a bad programming practice generally: variables should not just pop into existence like that. Just because you can do something does not make it a good idea!

If you take the time to read those links then people with more knowledge than me will explain why dynamically creating variables is a bad idea.

[John D'Errico]

@Nick - you are getting good advice from both responders. Please learn from it.

Your code will improve greatly, becoming more robust to bugs. It will be faster to write your code, no longer to need many different variables with all those names. And you can avoid all those otherwise necessary evals, a bad thing in general to use.