# How do I Average across structure

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Rene Sebena on 29 Aug 2018
Answered: Image Analyst on 30 Aug 2018
I have a 14 subject structure (ERP_data.ERP_data); for each subject there is 3D matrix: 32(electrode) x 381(data) x 32(condition); I would like to average the data across subjects with nanmean, so the final matrix will be 32x381x32; thank you for you help!
R
Rene Sebena on 29 Aug 2018
Sorry, but datafile is too big to upload...you can see the structure of that file on the picture.

Jacob Ward on 29 Aug 2018
Here's a possible solution I used to solve your problem:
clear; close all;
% This part just creates dummy data similar to yours with the same structure
ERP_data(14) = struct('ERP_data',0);
for n = 1:14
ERP_data(n) = struct('ERP_data',rand(32,381,32));
end
averagedData = zeros(32,381,32); % Initializes final matrix
for n = 1:32
for m = 1:381
for o = 1:32
dataToAverage = zeros(14,1); % Initializes vector to average
for p = 1:14
dataToAverage(p) = ERP_data(p).ERP_data(n,m,o); % Grabs the data point from each subject for the position given by m,n, and o
end
averagedData(n,m,o) = nanmean(dataToAverage); % Averages those points and then assigns that value to the position given by m,n, and o in the final matrix
end
end
end
Hope that helps!
Rene Sebena on 29 Aug 2018
Thanks a lot! This is what I did meanwhile, and it is also working:
GA_ERP_cue = []; for ch = 1:32 GA_ERP_cue_temp = nanmean([ERP_data(1).ERP_data(ch,:,:); ERP_data(2).ERP_data(ch,:,:); ERP_data(3).ERP_data(ch,:,:); ERP_data(4).ERP_data(ch,:,:); ERP_data(5).ERP_data(ch,:,:); ERP_data(6).ERP_data(ch,:,:); ERP_data(7).ERP_data(ch,:,:); ERP_data(8).ERP_data(ch,:,:); ERP_data(9).ERP_data(ch,:,:); ERP_data(10).ERP_data(ch,:,:); ERP_data(11).ERP_data(ch,:,:); ERP_data(12).ERP_data(ch,:,:); ERP_data(13).ERP_data(ch,:,:); ERP_data(14).ERP_data(ch,:,:)]); GA_ERP_cue(ch,:,:) = GA_ERP_cue_temp; end

Image Analyst on 30 Aug 2018
You can use mean() with the 'omitnan' option.