# How to put data from different structures in one matrix?

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Inti Vanmechelen on 17 Dec 2015
Answered: Guillaume on 17 Dec 2015
I'm working with EMG signals (data from 10 subjects for 3 motions) and when I filtered and normalized the data, I saved them in a structure. Example: EMGProcessed.(subjects{i}).(motion{k}).
Now I want to plot the average values of those EMG signals and I if I calculate the averages, I get one value for each subject, but I want to plot the averaged signal for all subjects in one plot. I can't figure out how to extract the data from the structures in a way I can get all the averages of the different subjects in one matrix.
Here's a part of my code:
Names = {'soleus_l' 'tib_ant_l' 'gas_lat_l' 'vas_lat_l' 'rect_fem_l' 'ham_lat_l'};
format = size(Names);
for k = 1:3
MeanResult.(motion{k}) = zeros(1,format(2));
StdResult.(motion{k}) = zeros(1,format(2));
for s =1:1:format(2)
IndexSoleus = find(Temp252==1)+1;
MeanSoleus = mean(EMGProcessed.(motion{k})(:,IndexSoleus));
StdSoleus = std(EMGProcessed.(motion{k})(:,IndexSoleus));
MeanResult.(motion{k})(1,s)=MeanSoleus;
StdResult.(motion{k})(1,s)=StdSoleus;
end
end
Obviously I get an the error that matlab can't find 'motion', beacause all my structures are saved as data.subjects.motion, but now I want the average motions for all the subjects and not for each subject.
I hope my explanation is understandable!

Guillaume on 17 Dec 2015
I know that a lot of people advocate using dynamic field names but in my opinion they are just as bad as dynamic variable names.
Anyway, assuming that all of the fields of your root EMGProcessed structure are indeed all subjects substructures with the same subfields:
for k = 1:3
mot = structfun(@(subject) {subject.(motions{k})}, EMGProcessed); %extract each subject motions{K} into a cell array
meanmotion{k} = mean(vertcat(mot{:})); %average the rows of the cell array
end
probably does what you want.

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