Log Function Conversion VBA

SBF12345

Well-known Member
Joined
Jul 26, 2014
Messages
614
I would like to convert nominal data values into logarithmic values to understand rates of change. The data is in the form of an array and I would like to observe the log values given the first nominal value in the series compared to the current value. What formula can I use to do this if I want to incorporate a first value and a current value? The code I have thus far is below.

The code structure may be misleading. I anticipate using both variables Array1 and Array2 to define a currently undefined Log variable associated with the current value (array2).

Code:
'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'X  This UDF converts an array of nominal values into an array of logarithmic values    X
'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX


Function LogPriceData(Arr As Variant, numberObs As Integer) As Variant


Dim yy As Integer
Dim Array1 As Integer
Dim Array2 As Integer


Array1 = Application.WorksheetFunction.Index(Arr, 1, 2)


For yy = 1 To numberObs


    Array2 = Application.WorksheetFunction.Index(Arr, yy, 2)
    


Next yy


End Function
 

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Can you show an example of input and expected results as it would appear on a worksheet?
 
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Sure,

The set of two columns on the left side are input type values and I would like to output values similar to the values in the set of two columns on the right.

The function I put together is below, but I'm getting an error on the LogArray(yy) line

Code:
Function LogPriceData(Arr As Variant, numberObs As Integer) As Variant

Dim yy As Integer
Dim Array1 As Integer
Dim Array2 As Integer
Dim LogArray As Variant


Array1 = Application.WorksheetFunction.Index(Arr, 1, 2)


For yy = 1 To numberObs


    Array2 = Application.WorksheetFunction.Index(Arr, yy, 2)
        
    LogArray(yy) = Application.WorksheetFunction.Log(Array2, Array1)


Next yy


LogArray = LogPriceData


End Function
 
Last edited:
Upvote 0
What are the inputs and what are the outputs? What is the calculation to arrive at the result?
 
Upvote 0
I used the worksheetfunction LOG() to produce the values. The first argument is the current value. The second argument is the base (first cell) written as $A$5

The inputs are taken from the left two columns the output is the right two columns.
 
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