NMath User's Guide

TOC | Previous | Next | Index

6.6 Vector Views (.NET, C#, CSharp, VB, Visual Basic, F#)

A variety of methods are providing for returning vector views of the data referenced by a matrix. The returned vector and the matrix share the data, so care must be exercised when modifying values. If after constructing a different view of an object's data you want your own private view that you can modify without affecting any other objects, simply invoke the DeepenThisCopy() method on the vector:

Code Example – C# matrix

var A = new DoubleMatrix( 8, 8, 1, 1 );

DoubleVector v = A.Diagonal();





v.DeepenThisCopy();




Code Example – VB matrix


Dim A As New DoubleMatrix(8, 8, 1.0, 1.0)




Dim V As DoubleVector = A.Diagonal()








V.DeepenThisCopy()




Row and Column Views


Member functions Row()
and Column() return vector views of a specified
row or column. For instance:


Code Example – C# matrix


var A = new DoubleMatrix( "3x3 [1 2 3  4 5 6  7 8 9]" );




     




DoubleVector row1 = A.Row( 1 );




DoubleVector col0 = A.Col( 0 );




Code Example – VB matrix


Dim A As New DoubleMatrix("3x3 [1 2 3  4 5 6  7 8 9]")








Dim Row1 As DoubleVector = A.Row(1)




Dim Col0 As DoubleVector = A.Col(0)




Diagonal Views


The Diagonal() member
function returns a vector view of a diagonal of a matrix. If no diagonal
is specified, a vector view of the main diagonal is returned. For example,
this code increments every element along the main diagonal:


Code Example – C# matrix


var A = new FloatMatrix( 5, 8 );




A.Diagonal()++;




Code Example – VB matrix


Dim A As New FloatMatrix(5, 8)




A.Diagonal().Increment()




Arbitrary Slices


The Slice() member function
returns a vector view of an arbitrary slice of a matrix. The parameters
are:


● the starting
row


● the starting
column


● the number
of elements


● the row
stride


● the column
stride


The slice begins at the starting row and column, and
extends for the number of elements. The increment between successive
elements in the vector is row stride rows and column stride columns.
For example, this code returns a view of the diagonal from the bottom
left corner to the top right of a 3x3 matrix:


Code Example – C# matrix


var A = new DoubleMatrix( "3x3 [1 2 3  4 5 6  7 8 9]" );




DoubleVector v = A.Slice( 2, 0, 3, -1, 1 );




Code Example – VB matrix


Dim A As New DoubleMatrix("3x3 [1 2 3  4 5 6  7 8 9]")




Dim V As DoubleVector = A.Slice(2, 0, 3, -1, 1)







Top

		


		
	

		

	


	



Top