DoubleMatrixVec(IndexCollection) Method

Returns a column vector obtained by stacking the specified elements of this instance.

Definition

Namespace: Novacta.Analytics
Assembly: Novacta.Analytics (in Novacta.Analytics.dll) Version: 2.1.0+428f3840cfab98dda567bb0ed350b302533e273a

C#

public DoubleMatrix Vec(
	IndexCollection linearIndexes
)

VB

Public Function Vec ( 
	linearIndexes As IndexCollection
) As DoubleMatrix

C++

public:
DoubleMatrix^ Vec(
	IndexCollection^ linearIndexes
)

F#

member Vec : 
        linearIndexes : IndexCollection -> DoubleMatrix

Parameters

linearIndexes IndexCollection: The linear indexes of the elements to stack.

Return Value

DoubleMatrix
A column vector obtained by stacking the specified elements of this instance.

Remarks

Let LaTeX equation be a matrix, and consider its generic entry

where and are the number of rows and columns of , respectively.

A linear index completely identifies an entry, assuming that entries are linearly ordered following the ColumnMajor data order. This means that entry LaTeX equation has linear index equal to , and matrix entries can be enumerated as follows:

where is the Count of the matrix.

Let LaTeX equation the collection of indexes represented by linearIndexes. This method, when called on a DoubleMatrix instance representing matrix , returns a new DoubleMatrix instance that represents a column vector, say , such that:

LaTeX equation

Example

In the following example, some matrix entries are vectorized.

C#

using System;

namespace Novacta.Analytics.CodeExamples
{
    public class VecExample1  
    {
        public void Main()
        {
            // Create a matrix.
            var data = new double[9] {
                1, 2, 3,
                4, 5, 6,
                7, 8, 9
            };
            var matrix = DoubleMatrix.Dense(3, 3, data, StorageOrder.RowMajor);
            Console.WriteLine("Initial data matrix:");
            Console.WriteLine(matrix);

            // Get the linear indexes of elements on
            // the main diagonal.
            var mainDiagonalIndexes = IndexCollection.Sequence(0, 4, 10);

            // Get the vectorization of the matrix main diagonal.
            var mainDiagonal = matrix.Vec(mainDiagonalIndexes);

            Console.WriteLine();
            Console.WriteLine("Vectorized main diagonal:");
            Console.WriteLine(mainDiagonal);

            // Entries can also be vectorized using a read-only wrapper of the matrix.
            ReadOnlyDoubleMatrix readOnlyMatrix = matrix.AsReadOnly();

            Console.WriteLine();
            Console.WriteLine("Vectorized main diagonal of a read-only data matrix:");
            Console.WriteLine(readOnlyMatrix.Vec(mainDiagonalIndexes));
        }
    }
}

// Executing method Main() produces the following output:
// 
// Initial data matrix:
// 1                2                3                
// 4                5                6                
// 7                8                9                
// 
// 
// 
// Vectorized main diagonal:
// 1                
// 5                
// 9                
// 
// 
// 
// Vectorized main diagonal of a read-only data matrix:
// 1                
// 5                
// 9                
// 
//

Exceptions

ArgumentNullException	linearIndexes is null.
ArgumentOutOfRangeException	linearIndexes contains an index which is greater than or equal to the Count of this instance.