Powerquery: Remove next n rows after occurence of value in column - powerquery

Question

I frequently have large datasets in powerquery where I need to remove/filter out the same row, as well as the following 13 whenever a certain value, in this case "Page" occurs. This occurs multiple times throughout the column.
I've tried referring to the next/previous rows by adding an index column and {[Index]+1} shenanigans but that either didn't work or took 15+ minutes to load.
I've tried setting up something with Table.RemoveFirstN(Text.Contains([Column], "Page"), 13) but that just errored out.
Would anyone know how I could filter the row where a value occurs, as well as the next n rows (index?) in Powerquery?
Kind regards,

Answer 1

This seems to work ok
We add an index. Test for "Page". In a new column, if Page is present, copy over the index. Fill down then group on that. Add 2nd index to the grouping. Expand all columns. Filter out anything where 2nd index is <14. Remove extra columns
let Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Merged Price Country", type text}}),
#"Added Index" = Table.AddIndexColumn(#"Changed Type", "Index", 1, 1),
#"Added Custom" = Table.AddColumn(#"Added Index", "Custom", each try if Text.Contains([Merged Price Country],"Page") then [Index] else null otherwise null),
#"Filled Down" = Table.FillDown(#"Added Custom",{"Custom"}),
mGroup = Table.Group(#"Filled Down", {"Custom"}, {{"Data", each Table.AddIndexColumn(_, "Index2", 1, 1), type table}}),
#"Removed Columns" = Table.RemoveColumns(mGroup,{"Custom"}),
// expand all columns
List = List.Union(List.Transform(#"Removed Columns"[Data], each Table.ColumnNames(_))),
#"Expanded Data" = Table.ExpandTableColumn(#"Removed Columns", "Data", List,List),
#"Filtered Rows" = Table.SelectRows(#"Expanded Data", each [Custom]=null or [Index2] > 14),
#"Removed Columns1" = Table.RemoveColumns(#"Filtered Rows",{"Index", "Custom", "Index2"})
in #"Removed Columns1"
I skipped out on using Table.RemoveFirstN() on the groupings in code above case there are leading rows you want to keep, but you could use that instead of adding the 2nd index and filtering like below
let Source = Excel.CurrentWorkbook(){[Name="Table3"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Merged Price Country", type text}}),
#"Added Index" = Table.AddIndexColumn(#"Changed Type", "Index", 1, 1),
#"Added Custom" = Table.AddColumn(#"Added Index", "Custom", each try if Text.Contains([Merged Price Country],"Page") then [Index] else null otherwise null),
#"Filled Down" = Table.FillDown(#"Added Custom",{"Custom"}),
mGroup = Table.Group(#"Filled Down", {"Custom"}, {{"Data", each Table.RemoveFirstN(_, 13), type table}}),
#"Removed Columns" = Table.RemoveColumns(mGroup,{"Custom"}),
// expand all columns
List = List.Union(List.Transform(#"Removed Columns"[Data], each Table.ColumnNames(_))),
#"Expanded Data" = Table.ExpandTableColumn(#"Removed Columns", "Data", List,List),
#"Removed Columns1" = Table.RemoveColumns(#"Expanded Data",{"Index", "Custom"})
in #"Removed Columns1"

Answer 2

Different approach. Wonder which might be faster:
Create a list of rows to be removed (by row number)
Select the rows not in that list
let
Source = Excel.CurrentWorkbook(){[Name="Table12"]}[Content],
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Text", type text}, {"Data", Int64.Type}}),
//Add index column
#"Added Index" = Table.AddIndexColumn(#"Changed Type", "Index", 0, 1, Int64.Type),
//create list rows to be removed
textCol = List.Transform(#"Added Index"[Text], each
if _ = null then null
else if Text.Contains(_,"Page",Comparer.OrdinalIgnoreCase) then "RemoveMe"
else _),
//create list of positions to be removed
removePos = List.Combine(List.Transform(List.PositionOf(textCol,"RemoveMe",Occurrence.All), each {_..List.Min({_+13, List.Count(textCol)})})),
//Filter the table using the "RemoveMe" list
filter = Table.SelectRows(#"Added Index", each not List.Contains(removePos,[Index])),
#"Removed Columns" = Table.RemoveColumns(filter,{"Index"})
in
#"Removed Columns"