Constructing names of array and structure variables

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!

Answer 1

[Stephen23]

"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:

https://www.mathworks.com/help/matlab/matlab_prog/fundamental-matlab-classes.html

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:

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

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.

[z8080]

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.