VB Cluster Example

Imports System

Imports CenterSpace.NMath.Core


Namespace CenterSpace.NMath.Examples.VisualBasic

  A .NET example in Visual Basic showing how to perform a hierarchical cluster analysis on a data set.
  Module ClusterExample

    Sub Main()

      Class ClusterAnalysis perform hierarchical cluster analysis. Instances 
      are constructed from a matrix of data, where each row represents an object
      to be clustered. This code clusters 8 random vectors of length 3:
      Dim Data As New DoubleMatrix(8, 3, New RandGenUniform())

      Console.WriteLine()
      Console.WriteLine("Data =")
      Console.WriteLine(Data.ToTabDelimited("F5"))

      Dim CA As New ClusterAnalysis(Data)

      The N property gets the number of objects clustered:
      Console.WriteLine("Number of objects clustered = " & CA.N)
      Console.WriteLine()

      Distances between objects are computed using a Distance.Function delegate.
      The default distance delegates is Distance.EuclideanFunction. Property
      Distances gets the vector of distances between all possible object pairs,
      computed using the current distance delegate. For n objects, the distance
      vector is of length (n-1)(n/2), with distances arranged in the order:
      (1,2), (1,3), ..., (1,n), (2,3), ..., (2,n), ..., ..., (n-1,n)
      Console.WriteLine("Results using Euclidean distance and Single linkage...")
      Console.WriteLine()
      Console.WriteLine("Distances: ")
      Console.WriteLine(CA.Distances.ToString("F3"))
      Console.WriteLine()

      Distances between clusters of objects are computed using a Linkage.Function
      delegate. The default linkage delegate is Linkage.SingleFunction.
      The Linkages property gets the complete hierarchical linkage tree, computed
      from Distances using the current linkage delegate. At each level in the tree,
      Columns 1 and 2 contain the indices of the clusters linked to form the next
      cluster. Column 3 contains the distances between the clusters.
      Console.WriteLine("Linkages: ")
      Console.WriteLine(CA.Linkages.ToTabDelimited("F3"))

      The CopheneticDistances property gets the vector of cophenetic distances
      between all possible object pairs. The cophenetic distance between two
      objects is defined to be the intergroup distance when the objects are first
      combined into a single cluster in the linkage tree. The correlation between
      the original Distances and the CopheneticDistances is sometimes taken as a
      measure of appropriateness of a cluster analysis relative to the original data:
      Dim R As Double = StatsFunctions.Correlation(CA.Distances, CA.CopheneticDistances)
      Console.WriteLine("Cophenetic correlation = " & R)
      Console.WriteLine()

      Delegates are provided as static variables on class Distance for
      euclidean, squared euclidean, city-block (Manhattan), maximum (Chebychev),
      and power distance functions. Delegates are provided as static variables
      on class Linkage for single, complete, unweighted average, weighted average,
      centroid, median, and Wards linkage functions. You can also easily create 
      your own distance or linkage functions. This code repeats the analysis using
      different distance and linkage delegates:
      CA.Update(Data, Distance.SquaredEuclideanFunction, Linkage.CompleteFunction)
      Console.WriteLine("Results using Squared Euclidean distance and Complete linkage...")
      Console.WriteLine()
      Console.WriteLine("Distances:")
      Console.WriteLine(CA.Distances.ToString("F3"))
      Console.WriteLine()
      Console.WriteLine("Linkages: ")
      Console.WriteLine(CA.Linkages.ToTabDelimited("F3"))

      The CutTree() method constructs a set of clusters by cutting the
      hierarchical linkage tree either at the specified height, or into the
      specified number of clusters. This code cuts the tree into 3 clusters:
      Console.WriteLine("CutTree() into 3 clusters...")
      Dim CS As ClusterSet = CA.CutTree(3)
      Console.WriteLine("Cluster each object is assigned to: " & CS.ToString())

      The indexer on ClusterSet gets the cluster to which a given object is
      assigned.
      Console.WriteLine("Object 0 is in cluster: " & CS(0))
      Console.WriteLine("Object 3 is in cluster: " & CS(3))

      The Cluster() method returns an array of integers identifying the objects
      assigned to a given cluster.
      Dim Objects As Array = CS.Cluster(1)
      Console.Write("Objects in cluster 1: ")
      Dim I As Integer
      For I = 0 To Objects.Length - 1
        Console.Write(Objects(I) & " ")
      Next
      Console.WriteLine()

      Console.WriteLine()
      Console.WriteLine("Press Enter Key")
      Console.Read()

    End Sub

  End Module

End Namespace