How to save inner loop data with outer loop data in one matfile

Hello Matlabers!

So basically i have this code

for i=1:5
    
    r=5;
    W = rand(m,r);
    H = rand(r,n);
    
    for rank=2:2:20  % Now for every value of rank I want to compute W0 and H0
      
          W0 = rand(m,rank);
          H0 = rand(rank,n);
    end
    
    % finally in the end I want to save all values. For each iteration of the OUTER loop, 
    % I will have all values of the INNER loop as well.
    
    save( ['DATA/data_',int2str(i),'.mat'],'W','H','W0','H0','-v7.3' )
    
    
end

So i wish to have my matfile contain files like

Data_1
    W,H
    W0_2,W0_4,W0_6,...,W0_20
Data_2
        W,H
    W0_2,W0_4,W0_6,...,W0_20
.
.
Data_5
        W,H
    W0_2,W0_4,W0_6,...,W0_20

[Stephen23]

"W0_2,W0_4,W0_6,...,W0_20"

Avoid creating variables with dynamic variable names:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

It is much simpler and much more efficient to use indexing.

Answer 1

[Stephen23]

Using a structure (or any other array) is better than using dynamically named variables:

m = 2;
n = 3;
r = 5;
V = 2:2:20;
for ii = 1:5
    W = rand(m,r);
    H = rand(r,n);
    S = struct();
    for jj = 1:numel(V)
        S(jj).W0 = rand(m,V(jj));
        S(jj).H0 = rand(V(jj),n);
    end
    F = fullfile('DATA',sprintf('data_%d.mat',ii));
    save(F,'W','H','S','V')
end

[fadams18]

Hello Thanks, I would like the W0 and H0 to be saved like the W and H and not into a structure. becaue i would want to load the mat files and use W0 and H0 as an input to a function later. is this possibe?

[Stephen23]

@fadams18: then use a cell array, or an ND array. Anything with indexing will be simple and efficient. I strongly recommend against forcing pseudo-indices or meta-data into variable names.

[fadams18]

@Stephen Please help a brother out :D. Im zero in matlab. How do I do that with a cell array or the ND array you suggest.

[Stephen23]

m = 2;
n = 3;
r = 5;
V = 2:2:20;
for ii = 1:5
    W = rand(m,r);
    H = rand(r,n);
    W0 = cell(1,numel(V));
    H0 = cell(1,numel(V));
    for jj = 1:numel(V)
        W0{jj} = rand(m,V(jj));
        H0{jj} = rand(V(jj),n);
    end
    F = fullfile('DATA',sprintf('data_%d.mat',ii));
    save(F,'W','H','W0','H0','V')
end

[fadams18]

Thank you so much.

[fadams18]

I Just appllied your idea. I am trying to load the files and you use them as input to my function NMF

function [] = runs(sNR,Mv,i,Tmax,passes)
 
    matcontent = fullfile('DATA', sprintf('data_%d_%d_%d.mat',sNR,Mv,i));
    load(matcontent,'Q','X','r','rank','W','H','W0', 'H0','V');
    for combidx = 1:numel(W0)  %try every combination
        %  index the cell arrays:
        
        [~,~,RRE_NMF,T_NMF]=NMF(X,Q,matcontent.Winit{combidx}, matcontent.Hinit{combidx},Tmax,passes);
        save( ['output/NMF_',int2str(sNR),'_',int2str(100*Mv),'_',int2str(rank),'_',int2str(i),'.mat'], 'RRE_NMF', 'T_NMF', '-v7.3' );
      
    end
end

When i run it, i get this error

Dot indexing is not supported for variables of this type.

[fadams18]

Dear Stephen Cobeldick

Could you kindly please help me with this question? https://fr.mathworks.com/matlabcentral/answers/444284-nested-loop-plots-help

Kind regards