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Constructing names of array and structure variables

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z8080
z8080 on 12 Aug 2021
Commented: z8080 on 13 Aug 2021
I'm trying to dynamically create variable names, for array and struc variables. However, my usual way (below) does not work, as the brackets and dots used in the names of struc array variables are not accepted:
>> varName = genvarname ( ['a(i,j).sampleNo' num2str(n) ] )
varName =
'a0x28i0x2Cj0x290x2EsampleNo2'
>> varToPlot = eval(varName)
Error using eval
Unrecognized function or variable 'a0x28i0x2Cj0x290x2EsampleNo2'.
Any suggestions? Thanks!

Accepted Answer

Stephen
Stephen on 12 Aug 2021
Edited: Stephen on 12 Aug 2021
"I'm trying to dynamically create variable names, for array and struc variables"
But your example shows you changing a structure fieldname, not a variable name. So your description does not match your example. It is not clear what you mean by "structure variables" as all structures are arrays, just like every other fundamental data type in MATLAB:
In any case, your EVAL-approach is slow, very ill-advised, counter-productive, and best avoided: https://en.wikipedia.org/wiki/Anti-pattern
The neat, simple, and very efficient MATLAB approach for the example you show is by using a dynamic fieldname:
For example:
F = sprintf('sampleNo%d',n);
varToPlot = a(i,j).(F)
Numbered fieldnames indicates poor data design which would be more efficiently accessed using indexing.
  1 Comment
z8080
z8080 on 13 Aug 2021
Thank you very much Stephen, you are right that my approach was quite suboptimal, and my description of it was inaccurate also. I've learnt something valuable from your answer.

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