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Excel Interpet Statistical Function converted to VB6

Posted on 2011-02-22
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Last Modified: 2013-11-26
I have and Excel spread sheet that has cells that containing the following values:
Known Y   Known X
2                6
3                5
9                11
1                7
8                5

In a cell I use the INTERCEPT function which Calculates the point at which a line will intersect the y-axes by using a best fit regression line plotted through the known x-values and y-values.

I need to do this in VB6 can you update the code below so that it will calculate the line of Intercept?

When it works correctly the Intercept value should equal 0.048387

Thanks
Public Function Intercept() As Double
  
  Dim KnownY(1 To 5) As Double
  Dim KnownX(1 To 5) As Double
  
  KnownY(1) = 2
  KnownY(2) = 3
  KnownY(3) = 9
  KnownY(4) = 1
  KnownY(5) = 8
  
  KnownX(1) = 6
  KnownX(2) = 5
  KnownX(3) = 11
  KnownX(4) = 7
  KnownX(5) = 5
  
  Intercept =

End Function

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Question by:xsawkins
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6 Comments
 
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Accepted Solution

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roger_karam earned 500 total points
ID: 34957128
I don't know if you can import the functions into regular VB, so here is the math solution for you following excel's explanation for the intercept function. You could also make it so it takes larger fields (more than 5 knowns) but this will do for your example:

Public Function Intercept() As Double
 
 Dim KnownY(1 To 5) As Double
  Dim KnownX(1 To 5) As Double
  Intercept = 0
 
  KnownY(1) = 2
  KnownY(2) = 3
  KnownY(3) = 9
  KnownY(4) = 1
  KnownY(5) = 8
 
  KnownX(1) = 6
  KnownX(2) = 5
  KnownX(3) = 11
  KnownX(4) = 7
  KnownX(5) = 5
 
  Dim dAverageY As Double
  Dim dAverageX As Double
  Dim dSlope As Double
  Dim dSlopeTop As Double
  Dim dSlopeBottom As Double
 
 
  dAverageY = 0
  dAverageX = 0
  dSlope = 0
 
  For i = 1 To 5
 
  dAverageY = dAverageY + KnownY(i)
  dAverageX = dAverageX + KnownX(i)
 
  Next i
 
  dAverageY = dAverageY / 5
  dAverageX = dAverageX / 5
 
 
  For i = 1 To 5
 
  dSlopeTop = dSlopeTop + ((dAverageX - KnownX(i)) * (dAverageY - KnownY(i)))
  dSlopeBottom = dSlopeBottom + (dAverageX - KnownX(i)) ^ 2
   
  Next i
 
  dSlope = dSlopeTop / dSlopeBottom
 
  For i = 1 To 5
 
  Intercept = Intercept + KnownY(i) - dSlope * KnownX(i)
   
  Next i
 
  Intercept = Intercept / 5

End Function
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Expert Comment

by:roger_karam
ID: 34957164
oh, my bad. if you are using VB 6, you need to switch the "Next i" statements for just "loop"

-RK
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LVL 5

Expert Comment

by:roger_karam
ID: 34957637
of course, if i totally understood you wrong and you are doing this in vba, just use:

intercept = Application.WorksheetFunction.Intercept(KnownY(), KnownX)
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Author Comment

by:xsawkins
ID: 34964849
Thanks for the input, let try this, this afternoon and I'll get back to you.
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LVL 100

Expert Comment

by:mlmcc
ID: 35213397
This question has been classified as abandoned and is being closed as part of the Cleanup Program. See my comment at the end of the question for more details.
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