How can I load .mat files?

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MByk
MByk on 14 Oct 2021
Commented: MByk on 19 Oct 2021
Hello, I have 3 .mat files and I want to measure feature importance. Following code works fine with .txt files but I am getting an error message with .mat files. I want to load all .mat files one by one and seperate predictors (X) and response variable (Y, the last column) for "fscchi2" function but I can't. How can I fix it?
matFiles = dir('Datasets/*.mat');
nFiles = length(matFiles);
for i = 1:nFiles
DataSet = load(matFiles(i).name);
X = DataSet(:,1:end-1);
Y = DataSet(:,end);
[~,Scores] = fscchi2(X,Y);
end
  4 Comments
Stephen
Stephen on 18 Oct 2021
"I couldn't find a way to seperate response column like I did with the .txt files"
The columns are in the structure field, not the structure itself. So you just need to access its field/s. If the fieldnames change (i.e. the data is very badly designed by someone who wants to make your life harder) then you can use dynamic fieldnames:
Rik showed this below.
Avoid loading directly into the workspace (as you show) unless you want to include latent bugs in your code.
Much simpler and more robust code would result if the data had been better designed (i.e. the same variable/field name).

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Accepted Answer

Rik
Rik on 18 Oct 2021
Or:
matfilenames={'Datasets/a.mat','Datasets/b.mat','Datasets/c.mat'};
for k = 1:3
S=load(matfilename{k});
fields=fieldnames(S);
data=s.(fields{1});
X = data(:,1:end-1);
Y = data(:,end);
[~,nCols] = size(X);
[Idx,Scores] = fscchi2(X,Y);
...
end
Next time, try to give the variables in your mat files the same name, so you can load to a struct array.
  6 Comments
MByk
MByk on 19 Oct 2021
I am a victim of misunderstanding. We had a communication problem. I am not a native speaker like you but I'm trying to do my best. My problem was reading .mat files sequentially and separating the last column and the rest into two different variables. I shared my code and a .mat file but they were deleted. Anyway seems like I had trouble explaining my problem. Your efforts were not futile and important for me.

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