RootX

The RootX control is utilized to find a root (zero crossing) of a user supplied function.  The control also has a routine for finding the minimum or maximum of a user supplied function.

RootX1.rootfind(initX1 As Double, initX2 As Double, xacc As Double, Xfinal As Double, Yfinal As Double, userfunc As Long) As Long
 
A simple example of root and min finding:

Sub findminroot()

Dim x1 As Double, x2 As Double, x3 As Double, xfinal As Double, yfinal As Double

' initial bracket 
x1 = -1000#
x2 = 1000#

' required accuracy
x3 = 0.0001

' find root (user supplied function roottest, below)
Call RootX1.rootfind(x1, x2, x3, xfinal, yfinal, AddressOf roottest)
MsgBox "Root X Y = " & xfinal & " " & yfinal

' find min (user supplied function mintest, below)
Call RootX1.minmaxfind(x1, x2, x3, xfinal, yfinal, AddressOf mintest)
MsgBox "Minimum X Y = " & xfinal & " " & yfinal

End sub

'Example user supplied functions

Function roottest(ByVal x As Double) As Double
     roottest = (x - 3.45)
End Function

Function mintest(ByVal x As Double) As Double
     mintest = (x - 3.45) ^ 2
End Function