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QuickStart Samples

Basic Matrices QuickStart Sample (Visual Basic)

Illustrates the basic use of the Matrix class for working with matrices in Visual Basic.

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Option Infer On

' The DenseMatrix class resides in the Extreme.Mathematics.LinearAlgebra namespace.
Imports Extreme.Mathematics
Imports Extreme.Mathematics.LinearAlgebra

Namespace Extreme.Numerics.QuickStart.VB
    ' Illustrates the use of the DenseMatrix class in the 
    ' Extreme.Mathematics.LinearAlgebra namespace of the Extreme Optimization
    ' Numerical Libraries for .NET.
    Module BasicMatrices

        Sub Main()
            '
            ' Constructing matrices
            '

            ' Option #1: specify number of rows and columns.
            ' The following constructs a matrix with 3 rows
            ' and 5 columns:
            Dim m1 = Matrix.Create(Of Double)(3, 5)
            Console.WriteLine("m1 = {0:F4}", m1)
            ' Option #2: specify a rank 2 Double array. 
            ' By default, elements are taken in column-major
            ' order. Therefore, the following creates a matrix
            ' with 3 rows and 4 columns:
            Dim m2 = Matrix.Create(New Double(,) _
             {
              {1, 2, 3},
              {2, 3, 4},
              {3, 4, 5},
              {4, 5, 6}
             })
            Console.WriteLine("m2 = {0:F4}", m2)
            ' Option #3: Specify component array, and number
            ' of rows and columns. The elements are listed
            ' in column-major order. The following matrix
            ' is identical to m2:
            Dim components As Double() = New Double() _
                {1, 2, 3, 2, 3, 4, 3, 4, 5, 4, 5, 6}
            Dim m3 = Matrix.Create(3, 4, components, MatrixElementOrder.ColumnMajor)
            Console.WriteLine("m3 = {0:F4}", m3)
            ' Option #4: same as above, but specify element
            ' order. The following matrix is identical to m4:
            Dim m4 = Matrix.Create(4, 3,
                components, MatrixElementOrder.RowMajor)
            Console.WriteLine("m4 = {0:F4}", m4)
            ' Option #5: same as #3, but specify whether to copy
            ' the matrix components, or use the specified array
            ' as internal storage.
            Dim m5 = Matrix.Create(3, 4, components, MatrixElementOrder.ColumnMajor, True)
            ' Option #6: same as #5, but specify whether to copy
            ' the matrix components, or use the specified array
            ' as internal storage.
            Dim m6 = Matrix.Create(4, 3,
                components, MatrixElementOrder.RowMajor, True)
            ' In addition, you can also create an identity 
            ' matrix by calling the static GetIdentity method.
            ' The following constructs a 4x4 identity matrix:
            Dim m7 = DenseMatrix(Of Double).GetIdentity(4)
            Console.WriteLine("m7 = {0:F4}", m7)

            '
            ' DenseMatrix properties
            '

            ' The RowCount and ColumnCount properties give the 
            ' number of rows and columns, respectively:
            Console.WriteLine("m1.RowCount = {0}", m1.RowCount)
            Console.WriteLine("m1.ColumnCount = {0}", m1.ColumnCount)
            ' The GetComponents method returns a one-dimensional
            ' Double array that contains the components of the 
            ' vector. By default, elements are returned in
            ' column major order. This is always a copy:
            components = m3.ToArray()
            Console.WriteLine("Components:")
            Console.WriteLine("components(3) = {0}", components(3))
            components(3) = 1
            Console.WriteLine("m3(0,1) = {0}", m3(0, 1))
            ' The GetComponents method is overloaded, so you can
            ' choose whether you want the elements in row major 
            ' or in column major order. The order parameter is
            ' of type MatrixElementOrder:
            components = m3.ToArray(MatrixElementOrder.RowMajor)
            Console.WriteLine("In row major order:")
            Console.WriteLine("components(3) = {0}", components(3))

            '
            ' Accessing matrix elements
            '

            ' The DenseMatrix class defines an indexer property 
            ' that takes zero-based row and column indices.
            Console.WriteLine("Assigning with private storage:")
            Console.WriteLine("m1(0,2) = {0}", m1(0, 2))
            ' You can assign to this property:
            m1(0, 2) = 7
            Console.WriteLine("m1(0,2) = {0}", m1(0, 2))

            ' The matrices m4 and m5 had the copy parameter in
            ' the constructor set to True. As a result, they
            ' share their component storage. Changing one vector
            ' also changes the other:
            Console.WriteLine("Assigning with shared storage:")
            Console.WriteLine("m4(0,0) = {0}", m7(0, 0))
            m5(0, 0) = 3
            Console.WriteLine("m4(0,0) = {0}", m7(0, 0))

            '
            ' Copying and cloning matrices
            '

            ' A shallow copy of a matrix constructs a matrix
            ' that shares the component storage with the original.
            ' This is done using the ShallowCopy method. Note
            ' that we have to cast the return value since it is
            ' of type MatrixBase, the abstract base type of all
            ' the matrix classes:
            Console.WriteLine("Shallow copy vs. clone:")
            Dim m10 = CType(m2.ShallowCopy(), DenseMatrix(Of Double))
            ' The clone method creates a full copy.
            Dim m11 = m2.Clone()
            ' When we change m2, m10 changes, but m11 is left
            ' unchanged:
            Console.WriteLine("m2(1,1) = {0}", m2(1, 1))
            m2(1, 1) = -2
            Console.WriteLine("m10(1,1) = {0}", m10(1, 1))
            Console.WriteLine("m11(1,1) = {0}", m11(1, 1))
            ' We can give a matrix its own component storage
            ' by calling the CloneData method:
            Console.WriteLine("CloneData:")
            m11.CloneData()
            ' Now, changing the original v2 no longer changes v7:
            m2(1, 1) = 4
            Console.WriteLine("m11(1,1) = {0}", m11(1, 1))

            Console.Write("Press Enter key to exit...")
            Console.ReadLine()
        End Sub

    End Module

End Namespace