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how to load saved workspace in a custom named variable?

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Hello,
this is what i am currently doing:
for i=1:length(A)
[y1,y2] = myfun(x,A)
savefile = ['test_'num2str(A(i)) '_and_' num2str(x) '.mat'] ;
save(savefile)
end
so i am currently saving all the workspace to a custom .mat file. Now i need to load those workspaces but i need to load them into struct variables that have the same name of the .mat file because i have a lot of data to work with. I tried with these:
for i=1:length(A)
['test_'num2str(A(i)) '_and_' num2str(x)] = load(['test_'num2str(A(i)) '_and_' num2str(x) '.mat']);
end
but it says: "Error: Assigning the function output to this expression is not supported."
how can i fix these problem?

  2 Comments

Stephen Cobeldick
Stephen Cobeldick on 20 Oct 2020
"i need to load them into struct variables that have the same name of the .mat file because i have a lot of data to work with."
That would be about the worst approach.
Don't paint yourself into a corner of writing slow, complex, inefficient code just to access your data:

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Accepted Answer

Stephen Cobeldick
Stephen Cobeldick on 20 Oct 2020
Edited: Stephen Cobeldick on 20 Oct 2020
The efficient approach is to use indexing (rather than anti-pattern dynamic variable names):
It is easy to import the file data into one cell array or one structure, e.g. the same one that dir returns:
D = 'absolute or relative path to the folder where the files are saved';
S = dir(fullfile(D,'*mat'));
for k = 1:numel(S)
F = fullfile(D,S(k).name);
S(k).data = load(F);
end
and then you can simply access the data from every file using basic and very efficient indexing, e.g. the third file:
S(3).name
S(3).data
If all of your .mat files contain variables with the same names (which is good data design) then you can also un-nest them by concatenating the data structures them into one non-scalar structure, e.g.:
out = [S.data]
out(3).someVariable
out(3).otherThing

  3 Comments

Davide Maglione
Davide Maglione on 20 Oct 2020
Thank you very much for your help! this is surely the best way.
Just one last thing, how can i save my workspace to a custom path? so when i do
S = dir(fullfile(D,'*mat'));
i can target with D a specific folder?
thank you again!
Stephen Cobeldick
Stephen Cobeldick on 20 Oct 2020
You can also use an absolute/relative filename when saving data, e.g.:
D = 'absolute or relative path to the folder where the files are saved';
F = sprintf('test_%d_and_%d.mat',A(i),x);
save(fullfile(D,F))

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More Answers (1)

Ameer Hamza
Ameer Hamza on 20 Oct 2020
Naming variables dynamically is not a good idea: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval. Just load it in a struct array or a cell array.
Struct array:
for i=1:length(A)
s(i) = load(['test_'num2str(A(i)) '_and_' num2str(x) '.mat']);
end
or a cell array
C = cell(length(A),1);
for i=1:length(A)
C{i} = load(['test_'num2str(A(i)) '_and_' num2str(x) '.mat']);
end

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