Top Pics - Sort on Recommended
I don't understand why, when viewing top picks, ordered by "recommended", movies aren't sorted by the star rating Movielens predicts for me. For instance, the first movie in my Top Picks has a prediction of 3.5 stars. The second movie has 4 stars. Further down there might be a movie with 4.5 stars.
Surely, when ordered by "recommended", it should be recommended by stars descending? Or how is it sorted?
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Howdy,
This can be a bit hard to explain, especially if you're interested in what we're doing at a low-mathematical level, but the basic idea can be boiled down to this: We view "recommendation" and "prediction" as two separate tasks. There's a lot of ways this can express itself, but a common example is the idea that a perfect prediction might (for example) give you 5-star predictions for the entire Lord of the Rings trilogy, but the prefect recommendation maybe doesn't want to waste 3 slots recommending a series of movies when it can instead recommend the first and then spend other recommendation space on movies you might like if you're not feeling like watching high fantasy today.
In our specific scenario -- recommendations are sorted by both predicted rating, as well as a user-controllable popularity factor. On average our users find that the "highest predicted" movies are sometimes a bit obscure, so blending with popularity can help bring a few more recognizable films into the recommendations. Since this feature is user-specific it can also be tuned to opposite way -- to suppress popular movies you might already know about and highlight more unexpected finds.
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sfdolon commented
I've wondered this at times too.