MATLAB: Concatenate Structures: select structures only if not empty.

concatenateisemptyMATLABstructures

I'd appreciate help on merging data from different sources. After importing the data, I store them in structures. One structure for each data source, each structure has the same fields. So, concatenating the structures into one is straight forward:
DataMerged = [Data1; Data2; Data3; Data4];
Now, the tricky part: For some data sets (experiments), one or several of these structures can be empty, i.e. contain not even any fields. How would I need to modify the code above to concatenate only those structures that are not empty? Currently, I use this work-around:
if ~isempty(test) && ~isempty(test2) && ~isempty(test3) && ~isempty(test4)
    listFiles = [test; test2; test3; test4];
    disp('Concatenate 1-4')
end
if ~isempty(test) && ~isempty(test2) && ~isempty(test3) && isempty(test4)
    listFiles = [test; test2; test3];
    disp('Concatenate 1-3')
end
and so on, for all combinations. Would you know a more elegant way of doing this?Thanks, for any help and suggestions,
ThorBarra

Best Answer

This clearly shows the drawback of naming your variables dynamically, like A1, A2, A3, A4. If you change, for instance, the way you import variables into your workspace, this would be a trivial, non-exisiting, problem.
Let's assume that you load the data like this or something similar:
Data1 = import('Exp1.dat')
Data2 = import('Exp2.dat')
Change this to a loop, and life becomes much measier:
Files = {'Exp1.dat', 'Exp2.dat'}
for k=1:numel(Files)
    Data{k} = import(Files{k}) ;
end
tf = ~cellfun(@isempty, Data)
AllData = [Data{tf}] ;
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