How to change the name of variables using a loop?

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Kathleen 2014-9-25

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编辑： Stephen23 2014-10-10

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.

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José-Luis 2014-9-25

编辑：José-Luis 2014-9-25

在 MATLAB Online 中打开

Are all those variables the same size? If so then just store them in an array:

 for ii = 1:n
     your_mat(:,ii) = something;
 end

Stephen23 2014-9-25

编辑：Stephen23 2014-10-10

在 MATLAB Online 中打开

José-Luis: good point. This should include array preallocation though:

   for ii = n:-1:1
       your_mat(:,ii) = something;
   end

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Answer 1

Stephen23 2014-9-25

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编辑：Stephen23 2014-9-25

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.

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Answer 2

Iain 2014-9-25

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在 MATLAB Online 中打开

Cells ARE the way to go.

Structures would be preferable to what you want

 mystruct.description = 'blah blah';
 mystruct = setfield(mystruct,['R_' num2str(ii) ], values);

However, sometimes, in rare cases, not using a monolithic storage solution is the only practical option. This option should be avoided whenever possible.

eval(['R_' num2str(ii) ' = values;']);

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Answer 3

Titus Edelhofer 2014-9-25

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Hi Kathleen,

why do you want to avoid cells? They are a perfect fit - and much cleaner/safer/easier to use than any clumsy and error prone variable creation based on names and indices ...?

Titus