How to change the name of variables using a loop?

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Kathleen
Kathleen 2014-9-25
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
José-Luis 2014-9-25
编辑：José-Luis 2014-9-25
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
Stephen23 2014-9-25
编辑：Stephen23 2014-10-10
José-Luis: good point. This should include array preallocation though:
for ii = n:-1:1
your_mat(:,ii) = something;
end

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Stephen23
Stephen23 2014-9-25
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.

更多回答（2 个）

Iain
Iain 2014-9-25
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;']);
Titus Edelhofer
Titus Edelhofer 2014-9-25
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

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