Question: What happens if a meta-data feature is specific for a single item or user?

[ilaria-speranza]

Hi!

I have a question about a sentence contained in LigtFM paper:

If the feature sets also contain meta-data features shared by more than one item or user, LightFM extends the MF model by letting the feature latent factors explain part of the structure of user interactions.

What happens if a meta-data feature is specific for a single item or user? Let's suppose for example to have 10 movies, 4 comedies, 5 horror, and 1 action and some users (with no metadata for simplicity) that interact with them.

Shall I encode action feature even it is specific of a single movie [method 1] or shall I drop that level and encode only comedy and horror [method 2]?

method 1: dataset.create_item_features({(1, ['comedy']), (2, ['comedy']), (3, ['comedy']), (4, ['comedy']), (5, ['horror']), (6, ['horror']), (7, ['horror']), (8, ['horror']), (9, ['horror']), (10, ['action'])})

method 2: dataset.create_item_features({(1, ['comedy']), (2, ['comedy']), (3, ['comedy']), (4, ['comedy']), (5, ['horror']), (6, ['horror']), (7, ['horror']), (8, ['horror']), (9, ['horror'])})

Many thanks Ilaria