public static Min ( Matrix source, VectorType t = VectorType.Col ) : |
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source | Matrix | |
t | VectorType | Use column or row (default: Col) |
return |
/// <summary> /// Summarizes a given Matrix. /// </summary> /// <param name="matrix">Matrix to summarize.</param> /// <param name="byVector">Indicates which direction to summarize, default is <see cref="VectorType.Row"/> indicating top-down.</param> /// <returns></returns> public static Summary Summarize(Matrix matrix, VectorType byVector = VectorType.Row) { return new Summary() { Average = matrix.Mean(byVector), StandardDeviation = matrix.StdDev(byVector), Minimum = matrix.Min(byVector), Maximum = matrix.Max(byVector), Median = matrix.Median(byVector) }; }
/// <summary> /// Generates a new Collaborative Filtering model. /// </summary> /// <param name="X">Training matrix values.</param> /// <param name="y">Vector of entity identifiers.</param> /// <returns></returns> public override IModel Generate(Matrix X, Vector y) { this.Preprocess(X.Copy()); // inputs are ratings from each user (X = entities x ratings), y = entity id. // create rating range in case we don't have one already if (this.Ratings == null) this.Ratings = new Range(X.Min(), X.Max()); // indicator matrix of 1's where rating was provided otherwise 0's. Matrix R = X.ToBinary(f => this.Ratings.Test(f)); // The mean needs to be values within rating range only. Vector mean = X.GetRows().Select(s => s.Where(w => this.Ratings.Test(w)).Sum() / s.Where(w => this.Ratings.Test(w)).Count() ).ToVector(); // update feature averages before preprocessing features. this.FeatureProperties.Average = mean; this.Preprocess(X); // where references could be user ratings and entities are movies / books, etc. int references = X.Cols, entities = X.Rows; // initialize Theta parameters Matrix ThetaX = Matrix.Rand(entities, this.CollaborativeFeatures, -1d); Matrix ThetaY = Matrix.Rand(references, this.CollaborativeFeatures, -1d); numl.Math.Functions.Cost.ICostFunction costFunction = new numl.Math.Functions.Cost.CofiCostFunction() { CollaborativeFeatures = this.CollaborativeFeatures, Lambda = this.Lambda, R = R, Regularizer = null, X = ThetaX, Y = X.Unshape() }; // we're optimising two params so combine them Vector Theta = Vector.Combine(ThetaX.Unshape(), ThetaY.Unshape()); numl.Math.Optimization.Optimizer optimizer = new numl.Math.Optimization.Optimizer(Theta, this.MaxIterations, this.LearningRate) { CostFunction = costFunction }; optimizer.Run(); // extract the optimised parameter Theta ThetaX = optimizer.Properties.Theta.Slice(0, (ThetaX.Rows * ThetaX.Cols) - 1).Reshape(entities, VectorType.Row); ThetaY = optimizer.Properties.Theta.Slice(ThetaX.Rows * ThetaX.Cols, Theta.Length - 1).Reshape(references, VectorType.Row); // create reference mappings, each value is the original index. this.ReferenceFeatureMap = (this.ReferenceFeatureMap == null ? Vector.Create(references, i => i) : this.ReferenceFeatureMap); this.EntityFeatureMap = (this.EntityFeatureMap == null ? Vector.Create(entities, i => i) : this.EntityFeatureMap); return new CofiRecommenderModel() { Descriptor = this.Descriptor, NormalizeFeatures = this.NormalizeFeatures, FeatureNormalizer = this.FeatureNormalizer, FeatureProperties = this.FeatureProperties, Ratings = this.Ratings, ReferenceFeatureMap = this.ReferenceFeatureMap, EntityFeatureMap = this.EntityFeatureMap, Mu = mean, Y = y, Reference = X, ThetaX = ThetaX, ThetaY = ThetaY }; }
/// <summary> /// Returns a vector of the minimum values for each row/column. /// </summary> /// <param name="source"></param> /// <param name="t"></param> /// <returns></returns> public static Vector Min(this Matrix source, VectorType t) { return(Matrix.Min(source, t)); }
/// <summary> /// A Matrix extension method that determines the minimum of the given parameters. /// </summary> /// <param name="source">The source to act on.</param> /// <returns>The minimum value.</returns> public static double Min(this Matrix source) { return(Matrix.Min(source)); }