Suppose that three subjects lets say A1, B1, and C1 belong to class 1 and A2 B2, and C2 belongs to class 2.
Then, feature extraction is applied on all A1 A2 B1 B2 C1 C2 to extract their features.
Now, I would like to know that should I model all features of class 1 together as a whole model or should I make a model for A1, make a model for B1, and make model for C1 and so on?
If a new subjects lets say D1 is missed in previous step, which approaches are better?
How about modelling time?
How about testing time?