MATLAB: How to change the name of variables using a loop

concatenateiterationnames

I need to do the same matrix calculations repeatedly, but I want to rename the variable within the loop. e.g. I need matrices R_1 R_2 R_3 R_4. I want to be able to set matrix R_1=( calcs for ii=1); R_2=( calcs for ii=2), etc. I know I can convert ii to a string using num2str(ii), but how do I concatenate that to R? R_ii=(calcs for ii)?

Am I going to need some sort of cell array to do that? I'm trying to avoid cells.

Best Answer

In MATLAB it is (almost always) better to not create variable names on the fly:

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

http://blogs.mathworks.com/videos/2010/03/08/top-10-matlab-code-practices-that-make-me-cry/

Use a cell or struct instead.

I know you were looking for a tidy solution... this is the tidy solution.

Related Solutions

MATLAB: Concatenate arrays within a loop,

Easy, given any number of arrays in a cell array C. You could use a loop like this, although it is inefficient because the output array is not preallocated:

C = {[1,2],[3,4],...} % cell array of arrays.
A = C{1};
for k = 2:numel(C)
    A = [A;C{k}];
end

Simpler and more efficient would be to concatenate them all at once, without a loop, e.g.:

A = vertcat(C{:})

Whatever you do, do NOT try to access variable names dynamically in a loop! Read this to know why:

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

Using an array (e.g. a cell array) and indexing is much simpler, neater, much more efficient, less buggy, and easier to debug.

MATLAB: Using a variable in an input prompt

    x = input(['What is the orientation of molecule ' num2str(ii) 'in the x-direction?']);

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Related Solutions

MATLAB: Concatenate arrays within a loop,

MATLAB: Using a variable in an input prompt

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