Mark rows depending on previous row

Hello Anonymous 

you can add a group-function and then with a Table.TransformColumns apply the necessary changes to the table.

Here the complete solution

let
	Source = #table
	(
		{"A","B"},
		{
			{"1","0"},	{"1","0"},	{"1","1"},	{"1","0"},	{"1","0"},	{"1","0"},	{"2","1"},	{"2","0"},	{"2","0"},	{"3","0"},	{"3","0"},	{"3","0"},	{"3","0"},	{"3","1"},	
			{"3","0"}
		}
	),
    Group = Table.Group(Source, {"A"}, {{"AllRowsB", each Table.SelectColumns(_, "B"), type table [A=text, B=text]}}),
	AddColumn = Table.TransformColumns
	(
		Group,
		{
			{
				"AllRowsB",
				each Table.ReplaceValue(Table.FillDown( Table.AddColumn(_,"C",(row)=> if row[B] = "1" then "2" else null), {"C"}), null, "0", Replacer.ReplaceValue, {"C"})
			}
		}
	),
    ExpandedAllRowsB = Table.ExpandTableColumn(AddColumn, "AllRowsB", {"B", "C"}, {"B", "C"})
in
    ExpandedAllRowsB

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Have fun

Jimmy