Recommendation-MovieRecommender

Movie Recommender

ML.NET version	API type	Status	App Type	Data sources	Scenario	ML Task	Algorithms
v1.0.0-preview	Dynamic API	up-to-date	End-End app	.csv	Movie Recommendation	Recommendation	Field Aware Factorization Machines

Overview

MovieRecommender is a simple application which both builds and consumes a recommendation model.

This is an end-end sample on how you can enhance your existing ASP.NET apps with recommendations.

The sample takes insipiration from the popular Netflix application and even though this sample focuses on movie recommendations, learnings can be easily applied to any style of product recommendations.

Features

• Wep app

  • This is an end-end ASP.NET app which presents three user profiles 'Ankit', 'Cesar', 'Gal'. It then provides these three users recommendations using a ML.NET recommendation model.

• Recommendation Model

  • The application builds a recommendation model using the MovieLens dataset. The model training code shows uses colloborative filtering based recommendation approach.

How does it work?

Model Training

Movie Recommender uses Colloborative Filtering for recommendations.

The underlying assumption with Colloborative filtering is that if a person A (e.g. Gal) has the same opinion as a person B (e.g. Cesar) on an issue, A (Gal) is more likely to have B’s (Cesar) opinion on a different issue than that of a random person.

For this sample we make use of the http://files.grouplens.org/datasets/movielens/ml-latest-small.zip dataset.

The model training code can be found in the MovieRecommender_Model.

Model training follows the following four steps for building the model. You can traverse the code and follow along.

Model Consumption

The trained model is consumed in the Controller using the following steps.

1. Create the ML.NET environment and load the already trained model

   // 1. Create the ML.NET environment and load the already trained model
   MLContext mlContext = new MLContext();
            
   ITransformer trainedModel;
   using (var stream = new FileStream(_movieService.GetModelPath(), FileMode.Open, FileAccess.Read, FileShare.Read))
   {
    trainedModel = mlContext.Model.Load(stream);
   }

2. Create a prediction function to predict a set of movie recommendations

   //2. Create a prediction function
   var predictionEngine = mlContext.Model.CreatePredictionEngine<MovieRating, MovieRatingPrediction>(trainedModel);
            
   List<(int movieId, float normalizedScore)> ratings = new List<(int movieId, float normalizedScore)>();
   var MovieRatings = _profileService.GetProfileWatchedMovies(id);
   List<Movie> WatchedMovies = new List<Movie>();

   foreach ((int movieId, int movieRating) in MovieRatings)
   {
     WatchedMovies.Add(_movieService.Get(movieId));
   }
   
   MovieRatingPrediction prediction = null;
   
   foreach (var movie in _movieService.GetTrendingMovies)
   {
       //Call the Rating Prediction for each movie prediction
        prediction = predictionEngine.Predict(new MovieRating
        {
            userId = id.ToString(),
            movieId = movie.MovieID.ToString()
        });
       //Normalize the prediction scores for the "ratings" b/w 0 - 100
       float normalizedscore = Sigmoid(prediction.Score);
       //Add the score for recommendation of each movie in the trending movie list
        ratings.Add((movie.MovieID, normalizedscore));
   }

3. Provide rating predictions to the view to be displayed

  ViewData["watchedmovies"] = WatchedMovies;
  ViewData["ratings"] = ratings;
  ViewData["trendingmovies"] = _movieService.GetTrendingMovies;
  return View(activeprofile);

Alternate Approaches

This sample shows one of many recommendation approaches that can be used with ML.NET. Depending upon your specific scenario you can choose any of the following approaches which best fit your usecase.

Scenario	Algorithm	Link To Sample
You want to use attributes (features) like UserId, ProductId, Ratings, Product Description, Product Price etc. for your recommendation engine. In such a scenario Field Aware Factorization Machine is a generalized approach you can use to build your recommendation engine	Field Aware Factorization Machines	This sample
You have UserId, ProductId and Ratings available to you for what users bought and rated. For this scenario you should use the Matrix Factorization approach	Matrix Factorization	Matrix Factorization - Recommendation
You only have UserId and ProductId's the user bought available to you but not ratings. This is common in datasets from online stores where you might only have access to purchase history for your customers. With this style of recommendation you can build a recommendation engine which recommends frequently bought items.	One Class Matrix Factorization	Product Recommender