# Basic Matrices in Visual Basic QuickStart Sample

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

' Illustrates the use of the DenseMatrix class in the
' Extreme.Mathematics.LinearAlgebra namespace of Extreme Numerics.NET.
Module BasicMatrices

Sub Main()
' The license is verified at runtime. We're using
' https://numerics.net/trial-key

'
' 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...")