计算加权标准偏差

Question

I want to calculate the weighted mean and weighted standard deviation. I was able to calculate the mean but not the standard deviation. How should I go about it?

     With Application.WorksheetFunction


        Range("AH" & 2) = .SumProduct(Columns(7), Columns(8)) / .Max(Columns(8))  'This code works very well. It calculates the mean


        Dim Nprime As Double

        Nprime = .CountIf(Range("H2:H" & lengthRows), "<>" & 0)  'This code works well


        Range("AM" & 2) = 2 * .SQRT(.SumProduct((Columns(7) - Columns(34)) ^ 2, Columns(8)) / ((Nprime - 1) * .Sum(Columns(8))) / Nprime) 'This line does not work. It should calculate the weighted standard deviation.

Range("AM" & 2) = Evaluate("2*SQRT(SumProduct((Columns(7) - weightedMean)^2), Columns(8)) / ((Nprime - 1) * .Sum(Columns(8))) / Nprime)") 'This line code evaluates with an answer of #VALUE! probably due to the titles in Row1, how do I fix the code to only evaluate the numerical values within the columns?

        End With

Answer 1

Not shure about the "weighted" AV or SD, but maybe you can adapt the following. Code loads data in an array, and then gets AV and SD.

Private Sub CommandButton1_Click()

    Dim MyArray() As Variant
    Dim lAV As Double
    Dim lSD As Double
    Dim i As Integer

    lLastRow = Worksheets("MyData").UsedRange.Rows.Count
    ReDim MyArray(1 To 1) As Variant

    For i = 1 To lLastRow
        MyArray(UBound(MyArray)) = Worksheets("MyData").Cells(i, 7).Value * Worksheets("MyData").Cells(i, 8).Value
        ReDim Preserve MyArray(1 To UBound(MyArray) + 1) As Variant 'now array is 1 element longer
    Next

    'Now MyArray contains desired data.
    'Get average and SD

    lAV = Application.WorksheetFunction.Average(MyArray)
    lSD = Application.WorksheetFunction.StDev(MyArray)

    'write results (be shure not to overwrite your data)
    Worksheets("MyData").Cells(1, 10) = "Average: "
    Worksheets("MyData").Cells(1, 11) = lAV
    Worksheets("MyData").Cells(2, 10) = "SD: "
    Worksheets("MyData").Cells(2, 11) = lSD
End Sub