How to calculate the evaluation metrics (i.e., F1 score) in leave one subject out cv when a subject belongs to single class only I have dataset of 10 subjects. the  dataset has 4 classess. 0,1,2 and 3. The distribution of  classes are not same. For example subject 1 does not have 1,2 and 3. It belongs to zeros class. currently I am evaluating the model using leave one subject out.In such scenario how to calculate the evaluation metrics like F1 score. I  tried the sklearn classification report but for  some subjects there are  only one class. shall I consider the macro F1 score?
You should not use summary statistics if you only have 10 data points. With that few datapoints, the summary statistics estimates will not be robust.