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Visual Basic(Microsoft) -VB.NET 2002-2008 FAQ
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Add-in and tools
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Extended DataTable Class
Posted: 9 Jan 04
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Hi all,
I seem to use the DataTable more than any other object, and I've been frustrated in the past by the lack of Search and Sort methods associated with it. So, I finally got brave and started working on it. My Sort and Search algorithms come from Data Structures in C++: Including Breadth & Laboratories by Angela Shiflet (Amazon page listed below). The statistical methods I wrote with the help of another Tek-Tips member, foundryqa. Hope this helps!
Ben
http://www.amazon.com/exec/obidos/ASIN/0314067442/qid%3...
Public Class SuperDataTable
Inherits System.Data.DataTable
'This class adds some Sort and Search Routines to the DataTable class, as
'well as some statistical methods.
#Region " Search & Sort Interface Functions "
Public Sub BubbleSort(ByVal KeyField As String)
Dim Done As Boolean
Dim i As Integer
Dim Max As Integer = Rows.Count - 2
Done = False
While Done = False
Done = True
For i = 0 To Max
If (Rows(i)(KeyField) > Rows(i + 1)(KeyField)) Then
Swap(i, i + 1)
Done = False
End If
Next i
Max -= 1
End While
End Sub
Public Sub SelectionSort(ByVal KeyField As String)
Dim i As Integer
Dim Index As Integer
For i = 0 To Rows.Count - 2
Index = GetMinAfter(KeyField, i)
Swap(i, Index)
Next
End Sub
Public Sub QuickSort(ByVal KeyField As String)
QSort(0, Rows.Count - 1, KeyField)
End Sub
Public Function BinarySearch(ByVal FieldName As String, ByVal SearchFor As Object) As Integer
'Be sure that the datatable is sorted by FieldName
Dim First As Integer = 0
Dim Last As Integer = Rows.Count - 1
Dim Key As Integer
While (True)
If First > Last Then Return -1
Key = First + ((Last - First) / 2)
If Rows(Key)(FieldName) = SearchFor Then Return Key
If Rows(Key)(FieldName) > SearchFor Then
Last = Key - 1
Else
First = Key + 1
End If
End While
End Function
Public Function SequentialSearch(ByVal FieldName As String, ByVal SearchFor As Object) As Integer
Dim i As Integer = 0
While i < Rows.Count
If Rows(i)(FieldName) = SearchFor Then Return i
End While
Return -1
End Function
#End Region
#Region " DataTable Statistical Methods "
Public Function StandardDeviation(ByRef ColumnName As String) As Double
Dim M As Double = 0
Dim Ct As Integer
Dim A As Double = 0
For Ct = 0 To Rows.Count - 1
M = M + Rows(Ct)(ColumnName)
Next
M = M / (Ct + 1)
For Ct = 0 To Rows.Count - 1
A = A + (Rows(Ct)(ColumnName) - M) ^ 2
Next
Return System.Math.Sqrt(A / (Ct + 1))
End Function
Public Function R_Squared(ByRef Xaxis As String, ByRef Yaxis As String) As Double
Dim n As Integer = Rows.Count
Dim a As Double = 0
Dim b As Double = 0
Dim c As Double = 0
Dim d As Double = 0
Dim e As Double = 0
Dim r As Data.DataRow
Dim r2 As Double = 0
For Each r In Rows
If (Not (r(Xaxis).GetType Is GetType(DBNull)) And (Not (r(Yaxis).GetType Is GetType(DBNull)))) Then
a = a + r(Yaxis)
b = b + r(Xaxis)
c = c + (r(Xaxis) * r(Yaxis))
d = d + (r(Yaxis) ^ 2)
e = e + (r(Xaxis) ^ 2)
End If
Next
r2 = (((n * c) - (a * b)) / ((((n * d) - (a ^ 2)) * ((n * e) - (b ^ 2))) ^ (0.5))) ^ 2
If Rows.Count > 1 Then
Return r2
Else
Return 0
End If
End Function
Public Function ArithmeticMean(ByRef ColumnName As String) As Double
Dim Sum As Double
Dim count As Integer
Sum = 0
For count = 0 To Rows.Count - 1
Sum = Sum + Rows(count)(ColumnName)
Next
ArithmeticMean = Sum / (count + 1)
End Function
Public Function Sum(ByVal Field As String) As Double
Dim S As Double
Dim x As Integer = 0
While x < Rows.Count
S += Rows(S)(Field)
x += 1
End While
Return S
End Function
#End Region
#Region " Helper Functions "
Private Sub QSort(ByVal first As Integer, ByVal last As Integer, ByVal Keyfield As String)
Dim loc As Integer
If first < last Then
loc = QPartition(first, last, Keyfield)
QSort(first, loc - 1, Keyfield)
QSort(loc + 1, last, Keyfield)
End If
End Sub
Private Function QPartition(ByRef first As Integer, ByRef last As Integer, ByVal KeyField As String) As Integer
Dim i As Integer = first
Dim loc As Integer = last + 1
Dim pivot As Object = Rows(first)(KeyField)
While i < loc
Do
i += 1
Loop While (Rows(i)(KeyField) < pivot) And i < last
Do
loc -= 1
Loop While Rows(loc)(KeyField) > pivot
If i < loc Then
Swap(i, loc)
End If
End While
Swap(first, loc)
Return loc
End Function
Private Function GetMinAfter(ByVal KeyField As String, ByVal i As Integer) As Integer
Dim M As Integer = i
Dim j As Integer
For j = i + 1 To Rows.Count - 1
If Rows(j)(KeyField) < Rows(M)(KeyField) Then
M = j
End If
Next
Return M
End Function
Private Sub Swap(ByRef j As Integer, ByRef k As Integer)
Dim x As Data.DataRow = NewRow()
Dim FieldNumber As Integer
For FieldNumber = 0 To Columns.Count - 1
x(FieldNumber) = Rows(j).Item(FieldNumber)
Rows(j)(FieldNumber) = Rows(k)(FieldNumber)
Rows(k)(FieldNumber) = x(FieldNumber)
Next
End Sub
#End Region
End Class
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