for loop with cell input parameter

Question

I have 4 data matrices 50x35 double (Diff_CT, Diff_Imp, Diff_F1, Diff_F2)

I have calculations to perform strictly identical for each of these matrices and suddenly I would like to create a for loop in which part of the name of the matrices is the input parameter

An example of what I tried but did not succeed

parameters = {'CT', 'Imp', 'F1', 'F2'};

for i_parameters = 1: numel(parameters)
    my_parameters = parameters{i_parameters};

    ['Diff_',(my_parameters),'_T0'] = ['Diff_',(my_parameters)](:,1) ['Diff_',(my_parameters)](:,8) ['Diff_',(my_parameters)](:,15) ['Diff_',(my_parameters)](:,22) ['Diff_',(my_parameters)](:,29)];
    ['DiffMean',(my_parameters),'0'] = mean(mean(['Diff_',(my_parameters),'_T0'));
    ['Diffstd',(my_parameters),'0'] = std(std(['Diff_',(my_parameters),'_T0'));
end

You should not be using multiple named matrices for this exact reason - it is not possible to elegantly loop over them. Rearrange your data using cell arrays or structs, instead. — nkjt
– nkjt, Commented Jun 17, 2018 at 18:13

Sardar Usama · Accepted Answer · 2018-06-18 09:05:19Z

There is never a good reason to create dynamic variable names. One of the problems they create is what you're experiencing. Use structs/ cell arrays/ ND arrays; whichever suitable for the situation. In your case, struct seems to be more suitable as shown below:

%Converting your data matrices into a struct
Diff_ = struct('CT',Diff_CT, 'Imp',Diff_Imp, 'F1',Diff_F1, 'F2', Diff_F2);  

for i_parameters = 1 : numel(parameters)       
    my_parameters = parameters{i_parameters}; 

    %Creating structures with your variables as their fields        
    Diff_.([my_parameters '_T0']) = [Diff_.(my_parameters)(:,1)  ...
        Diff_.(my_parameters)(:,8)  Diff_.(my_parameters)(:,15) ...
        Diff_.(my_parameters)(:,22) Diff_.(my_parameters)(:,29)];

    DiffMean.([my_parameters '0']) = mean(mean(Diff_T0.(my_parameters)));
    Diffstd.([my_parameters '0'])  = std(std(Diff_T0.(my_parameters)));
end

What you were expecting to have as the variables Diff_CT_T0, DiffMeanCT0 and DiffstdCT0 can now be accessed as Diff_.CT_T0, DiffMean.CT0 and Diffstd.CT0 respectively and so on.

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