Linear Interpolation in VBA

[annie_54]

Hey Everyone,

I have been working on a function to linear interpolate some data- I got it to where it was giving values however they seem to be incorrect. I cant find an error in the equation so far so i am not sure where to fix things.

I am also extremely new to VBA to bear with me on the code

Thanks for the help in advance!
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Dim X1 As Double, X2 As Double, X3 As Double, Y1 As Double, Y3 As Double


ThisWorkbook.Activate
' X1 is used as the smallest x value
Application.ActiveCell.Activate
X1 = ActiveCell.Value
' X is used as the middle value
Application.ActiveCell.offset(1, 0).Activate
X = ActiveCell.Value
' X2 is used as the largst x value
Application.ActiveCell.offset(1, 0).Activate
X2 = ActiveCell.Value
' Y1 is used as the smallest Y value
Application.ActiveCell.offset(-2, 1).Activate
Y1 = ActiveCell.Value2
' Y2 is used as the largest Y value
Application.ActiveCell.offset(2, 0).Activate
Y2 = ActiveCell.Value2


Dim Pt1 As String, Pt2 As String, Pt3 As String


Pt1 = (X - X1)
Pt2 = (Y2 - Y1)
Pt3 = (X2 - X1)




MsgBox "" & Y1 + Pt1 * (Pt2 \ Pt3)




End Function
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[Fazza]

welcome, Annie

Please post a sample of the input data. What values are in what cells, and maybe describe what each value means if it might aid understanding.

And then explain what the result is for those inputs and where/how it will be used.

regards, Fazza

 

[sykes]

Can you also post the first part of your code - possibly only one line from the top (Public Function, perhaps?
Also, where does this code reside? in a code module, or worksheet module, or ThisWorkbook module?