14 Jul 2017

Excel VBA User Defined Function for Transformation of Braun-Blanquet Values to Precentages of Vegetation Cover

Function Transf_BraunBlanquet(ByVal BB_Str As String) As String

'Transformation of Braun-Blanquet 'Artmächtigkeit' to percentage cover (similar to usage in TurboVeg or twinspan)
'The key value mapping can be altered depending on specific requirements
'This UDF is used in the UDF SumKum_BraunBlanquet(), which will apply the Transformation on a range of values and
'will sum the transformed percentages. This cumulative sum can be used to check if the Braun-Blanquet estimation for
'a vegetation layer is reasonable.

    With CreateObject("Scripting.Dictionary")
        '~~> first transfer your list in Dictionary
        .Add "r", "0"
        .Add "+", "0"
        .Add "1", "1"
        .Add "2m", "2"
        .Add "2a", "10"
        .Add "2b", "20"
        .Add "3", "37,5"
        .Add "4", "67,5"
        .Add "5", "87,5"
        If Len(BB_Str) = 0 Then
        '~~> case: empty cell
            Transf_BraunBlanquet = 0
            Exit Function
        End If
        For Each elem In .keys
            key = elem
            If key = BB_Str Then
                Transf_BraunBlanquet = .Item(elem) * 1
                Exit Function
            End If
        Next elem
    End With
End Function

Function SumKum_BraunBlanquet(Rng As Range) As Double
'See comments on Transf_BraunBlanquet() for explanations

    Dim Sum As Double
    Dim RngArr As Variant
    RngArr = Application.Transpose(Rng) 'dumps range values to array
    For Each elem In RngArr
        Sum = Sum + Transf_BraunBlanquet(elem)
    Next elem
    SumKum_BraunBlanquet = Sum
End Function