by Ralf Kriegel (1 Submission)
Category: Math/Dates
Compatability: Visual Basic 3.0
Difficulty: Intermediate
Date Added: Wed 3rd February 2021
Rating: 
(5 Votes)
Calculation of a linear regression
(straight line) using a X,Y data array
Inputs
X,Y data array
Assumes
requires a minimum of two data points
Code Returns
Slope and Y-intersection
Side Effects
nothing
API Declarationsnothing
VBcodersPublic Sub LinRegsngArr(ByRef sng_XArray!(), ByRef sng_YArray!(), _
ByVal lowLimInd&, ByVal uppLimInd&, ByRef Slope!, ByRef YSection!)
'this Code calculates a linear regression
'using the points of two Arrays (X,Y)
'and gives back slope and Y-intersection
'of the straight line
Dim sng_XSum!, sng_YSum!, sng_XQuad!, sng_YQuad!, sng_XYProd!, sng_Fract!
Dim lng_Index&, ValuesCounts&, sng_Zaehler!
ValuesCounts = uppLimInd - lowLimInd + 1
For lng_Index = lowLimInd To uppLimInd
sng_XSum = sng_XSum + sng_XArray(lng_Index)
sng_YSum = sng_YSum + sng_YArray(lng_Index)
sng_XQuad = sng_XQuad + sng_XArray(lng_Index) ^ 2
sng_YQuad = sng_YQuad + sng_YArray(lng_Index) ^ 2
sng_XYProd = sng_XYProd + sng_YArray(lng_Index) * sng_XArray(lng_Index)
Next
sng_Fract = ValuesCounts * sng_XQuad - sng_XSum ^ 2
Slope = (ValuesCounts * sng_XYProd - sng_XSum * sng_YSum) / sng_Fract
YSection = (sng_YSum * sng_XQuad - sng_XSum * sng_XYProd) / sng_Fract
End Sub
