--- a
+++ b/Feature Extraction/extractPSD.m
@@ -0,0 +1,32 @@
+function X=extractPSD(x_train,startS,endS,wStep,wRange)
+Fs=1;   % sampling frequency (seconds)
+
+FS=128;
+
+N=size(x_train,3);
+sz=floor((endS-(startS+wRange))/wStep)+1;
+X=zeros(sz*FS,2);
+cn=0;
+for i=1:N
+    
+    for sig=startS:wStep:endS-wRange
+        
+        sW=sig*FS+1;
+        eW=(sig+wRange)*FS;
+        
+        C3Sig=x_train(sW:eW,1,i);
+        C4Sig=x_train(sW:eW,3,i);
+        
+        [pxx3, ~] = pwelch(C3Sig,[],[],[],Fs);
+        [pxx4, ~] = pwelch(C4Sig,[],[],[],Fs);
+        
+        cn=cn+1;
+        X(cn,1)=sum(pxx3);
+        X(cn,2)=sum(pxx4);
+        
+    end
+end
+
+end
+
+