Stuck trying to cathegorize values in a column

[Myagi-Do]

I am trying to categorize values (for a lack of better wording) in a column. I want to increase a counter if a new value is detected. 

The "Goal" column is what I am trying to build. I thought of copying values with a -1 shift but I am stuck now on creating a counter and increasing this counter when Values and Custom don't match. Total newbie here 🙂  Any help is appreciated.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjRU0lEyVIrVIYJpBGIakcw0NTUzB3KMMTkWlkCmCTWYsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Values = _t, #"Goal" = _t]),
    #"Added Index" = Table.AddIndexColumn(Source, "Index", 0, 1, Int64.Type),
    #"Changed Type" = Table.TransformColumnTypes(#"Added Index",{{"Values", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each List.Range(
   #"Changed Type"[Values],
   [Index]-1,
   1)),
    #"Extracted Values" = Table.TransformColumns(#"Added Custom", {"Custom", each Text.Combine(List.Transform(_, Text.From)), type text}),
    #"Replaced Errors" = Table.ReplaceErrorValues(#"Extracted Values", {{"Custom", null}})
in
    #"Replaced Errors"

  

[Vijay_A_Verma · Accepted solution]

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test (later on when you use the query on your dataset, you will have to change the source appropriately)

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjRU0lEyVIrVIYJpBGIakcw0NTUzB3KMMTkWlkCmCTWYsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Values = _t, #"Goal" = _t]),
    #"Removed Columns" = Table.RemoveColumns(Source,{"Goal"}),
    #"Grouped Rows" = Table.Group(#"Removed Columns", {"Values"}, {{"Temp", each _, type table [Values=nullable text]}}),
    #"Added Index" = Table.AddIndexColumn(#"Grouped Rows", "Index", 1, 1, Int64.Type),
    #"Expanded Temp" = Table.ExpandTableColumn(#"Added Index", "Temp", {"Values"}, {"Values.1"}),
    #"Removed Columns1" = Table.RemoveColumns(#"Expanded Temp",{"Values.1"}),
    #"Renamed Columns" = Table.RenameColumns(#"Removed Columns1",{{"Index", "Goal"}})
in
    #"Renamed Columns"