MovieRecommender: BuildTrainModel code

Program.cs

        public static ITransformer BuildTrainModel(MLContext mlContext, IDataView trainingDataView)
        {
            var catalog = mlContext.Transforms.Conversion;

            IEstimator<ITransformer> estimator = catalog.MapValueToKey(outputColumnName: "userIdEncoded", inputColumnName: "userId")
                .Append(catalog.MapValueToKey(outputColumnName: "movieIdEncoded", inputColumnName: "movieId"));

            var options = new MatrixFactorizationTrainer.Options
            {
                MatrixColumnIndexColumnName = "userIdEncoded",
                MatrixRowIndexColumnName = "movieIdEncoded",
                LabelColumnName = "Label",
                NumberOfIterations = 20,
                ApproximationRank = 100
            };

            var trainerEstimator = estimator.Append(mlContext.Recommendation().Trainers.MatrixFactorization(options));

            Console.WriteLine("=============== Training the model ===============");
            ITransformer model = trainerEstimator.Fit(trainingDataView);

            return model;
        }