Clarification on Metrics Calculation in EvaluatePrequential with Missing Classes in Chunks

[Salah Uddin]

Hello,

I have a question regarding how EvaluatePrequential in MOA calculates metrics when a class is not present in some chunks.

For example, let's say we have five classes: A, B, C, D, and E, and the sample frequency is set to 500 instances. If, in one chunk, classes D and E are not present, how are the precision, recall, and F1-score calculated for these classes? Are these metrics computed based on the available classes in the chunk, or does MOA handle the absence of certain classes in the calculation in a different way?

Any insights would be greatly appreciated!

Thank you!