Extract value from every struct

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I have four 1x1 struct files like the attached. mat file in every 60 subfolder, I want to extract the u field in each struct and assign its name to it. The name is in a field called name e.g, the name of this one is rdf. Then use it as one of the X e.g (model = fitcsvm(X,Y, 'KernelFunction','linear', 'BoxConstraint',1);) for svm classification. where, X= [X1 X2 X3 X4] and X1 is currently rdf. Using a for loop, please how do I extract something from a struct.

Accepted Answer

Walter Roberson
Walter Roberson on 4 Aug 2022
Edited: Walter Roberson on 6 Aug 2022
vois={'ldF', 'rdF', 'lvF', 'rvF'};
numvois = length(vois);
basedir = 'place/where/the/folders/are';
foldinfo = dir(basename);
foldinfo(~[foldinfo.isdir]) = []; %remove non-folders
foldinfo(ismember({foldinfo.name}, {'.', '..'})) = []; %remove . and ..
foldernames = fullfile({foldinfo.folder}, {foldinfo.name});
numfolders = length(foldernames);
X_all = cell(numfolders, numvois);
for K = 1 : numfolders
thisfolder = foldernames{K};
[~, basename, ~] = fileparts(thisfolder);
for vidx = 1 : numvois
filename = fullfile(thisfolder, basename + "_" + vidx + ".mat");
Features = load(filename);
X_i = Features.xY.u;
X_all{thisfolder, vidx} = X_i;
end
end
At the end of this, X_all will be a cell array with as many rows as folders (60, you said), and as many columns as vois (4)
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More Answers (2)

Karim
Karim on 2 Aug 2022
Edited: Karim on 2 Aug 2022
You can acces the data in the struct by placing a point after the variable name of the struct, follewed by the fieldname you want to acces. See below for an example for the 'u' variable.
Features = load(websave('myFile', "https://nl.mathworks.com/matlabcentral/answers/uploaded_files/1085720/VOI_rdF_1.mat"));
% first extract xY from 'Features'
xY = Features.xY;
% then extract u from the struct
u = xY.u;
% plot the data
figure
plot(u)
grid on

Monalisa Chikezie
Monalisa Chikezie on 2 Aug 2022
Edited: Walter Roberson on 4 Aug 2022
Hi, thanks for the respnse.
this is what I have so far, but it seems to give an error.
vois={'ldF', 'rdF', 'lvF', 'rvF'};
for j=1:4
Features = load(pwd, '_1.mat'));
X_i=Features.xY.u;
X_all(:)=X_i;
  7 Comments
Monalisa Chikezie
Monalisa Chikezie on 3 Aug 2022
to capture all of the 4 vois in each of the 60 folders

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