I have a question regarding application of tf-idf.
Let's assume I have a document classification task, there is a training set of documents that are multi-labeled, such that one document can have multiple labels. I use bigrams and unigrams as a features and tf-idf as features values.
The question is, how to calculate td-idf values.
For example I have document 1 that classified as class1 and class2.
tf should be just the frequency of feature f in document 1 or frequency of feature f in all documents of type class1 and class2 or frequency of feature f in the entire corpus?
The same question regarding idf. Should I consider the class of dicument when calculating it?