How do you populate a struct with multiple loaded .mat files?

Hi,

So I have this code below that loads my data. It works fine when not wrapped in a function, however when I wrap it in a function it doesn't work. While debugging, I can see it loading my files, however, when I get to the end of the function, they don't load onto the current workspace.

Secondly, when I assign a variable for the data files to load into, they load fine when I am only dealing with one file. When I try to load multiple files however, it doesn't run as expected. It keeps overwriting each loaded array in the struct.

I'm not at all sure what i'm doing wrong

Any help is appreciated.

Thank you!

function S=LoadData % When not wrapped in function, doesn't output S
[file,path]=uigetfile(...
    {'*.m;*.mlx;*.fig;*.mat;*.slx;*.mdl',...
    'MATLAB Files (*.m,*.mlx,*.fig,*.mat,*.slx,*.mdl)';
    '*.jpg;*.jpeg;*.png;*.tif;*.tiff',...
    'Images (*.jpg,*.jpeg,*.png,*.tif,*.tiff)'},...
    'Select a File','MultiSelect','on');
if isequal(file,0)
    clear file
    clear path
else
    if iscell(file)
        for k=1:size(file,2)
            S=load(fullfile(path,file{k})); % Keeps overwriting S rather than appending
        end
    else
        S=load(fullfile(path,file));
    end
    clear file
    clear path
end

end

Answer 1

[Xingwang Yong]

There is a contradiction between your statement and your comment in code. I assume you are asking about " however when I wrap it in a function it doesn't work".

In your case, the scope of variable 'S' is limited within the function LoadData(). You can use nested function to change this behaviour.

function yourMainScript
S = [];
S = LoadData(); % now S will be in the workspace of the main script
    function S=LoadData
        % ...
    end
end

As for overwriting, you can avoid it like this

if isempty(S)
    S = load(fullfile(path,file{k}));
else
    tmp = load(fullfile(path,file{k}));
    for fn = fieldnames(tmp)'
         S.(fn{1}) = tmp.(fn{1}); % this will overwrtie if have same fieldnames
    end
end

Loop over fields of a struct can be found here:

https://www.mathworks.com/matlabcentral/answers/229604-how-to-copy-field-contents-of-one-struct-to-another#answer_185865

[David Mabwa]

Thank you, that worked like a charm. My main issue was with the overwriting.