Group by with variable columns

Hello - this is how you can group and sum a variable number of columns... Included in the sample script below shows an example of how you can sum the values of all numeric data fields and another example of how you can sum the values of all fields beginning with "xba". 

SCRIPT

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WclTSUTI2AhKGIMLMVClWByJoCsQW5kDCyAQhBhI0NwNpMYYLgvlGxkDCBKHb2ABqhKWFUmwsAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ColumnName1 = _t, #"xba-1" = _t, #"xba-2" = _t, #"xba-3" = _t]),
    ChangedType = Table.TransformColumnTypes(Source,{{"xba-1", Int64.Type}, {"xba-2", Int64.Type}, {"xba-3", Int64.Type}}),
    Grouped = Table.Group(ChangedType, {"ColumnName1"}, {{"Data", each _, type table }}),
    // Use this line to select all columns that are of type number.
    // ListOfColumnNames = Table.ColumnsOfType ( Grouped[Data]{0}, {type nullable number} ),
    // Use this line to select all columns beginning with xba.
    ListOfColumnNames = List.Select ( Table.ColumnNames ( Grouped[Data]{0} ), each Text.StartsWith ( _, "xba" ) ),
    SumGroupedData = Table.AddColumn ( 
        Grouped, 
        "SummedData", each 
        Table.FromRows ( 
            { 
                List.Transform ( 
                    Table.ToColumns ( 
                        Table.SelectColumns ( [Data], ListOfColumnNames ) 
                    ), each try List.Sum ( _ ) otherwise _ 
                ) 
            }, ListOfColumnNames 
        ) 
    ),
    Expand = Table.ExpandTableColumn(SumGroupedData, "SummedData", ListOfColumnNames)
in
    Expand

RESULT