MATLAB: Change array name inside loop, external data

cell arraysfor loopindexingMATLABstructures

I'm working with a data set of around 50 Gb so i decided to work by "pieces" calling and eliminating each data set after each calculation has been performed. I have 8 different .mat files, each one containing a cell{1,5} that contains each an array of (1,50) and finally a 2d array of (1024,1024). My question is, can i change somehow the name of the array containing this data inside the calculation loop? Code is below. I have read similar questions, but no similar approach to my problem, the cell arrays i'm trying to read and calculate have already an assigned name.
ld = [5,10,15,20,25,50,75,100];
for i=1:8
    load(sprintf('U%i.mat',ld(i)));
    for a = 1:1024
        for b = 1:1024
            for c = 1:50
                stad_pmmh(c) = 'U_%i{c}(a,b);   %%%%Here is the main issue and where i need a "dynamical naming"
            end
            STAD_pmmh{a,b} = stad_pmmh;
            dev_pmmh(a,b) = std(STAD_pmmh{a,b});
        end
    end
    save(sprintf('dev_%i',ld(i)),'dev_pmmh');
%     
    clear (sprintf('U_%i',ld(i)));
end

Best Answer

Dynamic naming and directly calling load() without any output argument is never a good idea: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval. If the files 'U%i.mat' only contains a single variable, then the following approach will be more suitable.
Change the load() line to
data = load(sprintf('U%i.mat',ld(i))); % data is a struct
f_name = fieldnames(data)
and the load the data like this
stad_pmmh(c) = data.(f_name{:})(a,b);
However, this will fail if the .mat files have multiple variables.
In that case, you will eventually use eval() to create the variable names dynamically, for example using sprintf: https://www.mathworks.com/help/matlab/ref/eval.html
stad_pmmh(c) = eval(sprintf('U_%i{c}(a,b)', i));
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