Concatenate Structures: select structures only if not empty.
2 views (last 30 days)
Show older comments
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
0 Comments
Accepted Answer
Jos (10584)
on 4 May 2019
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}] ;
2 Comments
Jos (10584)
on 6 May 2019
You're welcome :-)
Another suggestion: use fullfile to create filenames:
fullfile(dataPath_XPS, '**', 'N*.ibw')
More Answers (1)
Walter Roberson
on 4 May 2019
Create a template that has all of the fields but no contents, such as
template_struct = struct('filename', [], 'is_loaded', [], 'SNR', []);
If you check with size() and fieldnames() you will see that this will be a struct of size 0 but which has the right fields.
Then
if isempty(test); test = template_struct; end
if isempty(test2); test2 = template_struct; end
if isempty(test3); test3 = template_struct; end
if isempty(test4); test4 = template_struct; end
DataMerged = [test1; test2; test3; test4];
1 Comment
Walter Roberson
on 4 May 2019
Or just use:
DataMerged = [];
if ~isempty(test); DataMerged = [DataMerged; test]; end
if ~isempty(test2); DataMerged = [DataMerged; test2]; end
etc
See Also
Categories
Find more on File Name Construction in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!