Find position number for each group (Table.PositionOf() with Table.Group) in Power Query (M language)

Question

I'd like to find number of position first "TAK" in column "taknie" for each group (column Grupa).

This is my table.

Grupa	taknie
g1	NIE
g1	TAK
g2	NIE
g2	NIE
g2	NIE
g2	TAK
g3	TAK
g3	TAK
g3	NIE
g3	TAK
g4	NIE
g4	TAK
g4	TAK
g5	NIE

I've tried in Advanced editor

let
    Source = Excel.CurrentWorkbook(){[Name="Tabela1"]}[Content],
    Grupa = Table.Group(Source, "Grupa", {"wynik", each Table.PositionOf(
        Source, 
        [taknie = "TAK"], 
        Occurrence.First,
        "taknie"
    ) + 1})
in
    Grupa

but it doesn't work properly:

enter image description here

Instead of 2, 2, 2, 2, 2, should be

Grupa	wynik
g1	2
g2	4
g3	1
g4	2
g5	0

Answer 1

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSjdUUNJR8vN0VYrVgfFCHL0hPCMUOYI8uD5jQjy4PlQ5ExQ5E0w5OM8UrjIWAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Grupa = _t, taknie = _t]),
    #"Grouped Rows" = Table.Group(Source, {"Grupa"}, {{"First", each List.PositionOf  ([#"taknie"], "TAK")+1, type nullable text}})
in
    #"Grouped Rows"