DO NOT USE EVAL.
Dynamically naming variables (and subsequently using eval) is not a good coding practice. That is explained in length here - https://in.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval
This (official) documentation page also advices to avoid using eval for the same - https://in.mathworks.com/help/matlab/matlab_prog/string-evaluation.html
A robust alternative (for reading data into MATLAB) is to read the data using the appropriate function, e.g - load for .mat files, and readtable/readmatrix/readcell for various different file formats.
If you want to access data from an existing variable in MATLAB, use indexing.
