Create numbering for active Row-1 as -1

[PB41091]

I have a data set. I have created column Flag for identifying difference days whereever is 30. Now I have to create a column where 1 row immediately before flag 1 should be -1 and flag 1 should be 0.

A	B	C	Date	DifferenceDays	Flag
a	p	N	5/31/2017	[Null]	[Null]
a	q	N	5/31/2020	1096	[Null]
a	r	Y	6/30/2020	30	1
a	s	Y	3/31/2022	639	[Null]
b	t	N	10/31/2020	[Null]	[Null]
b	u	Y	11/30/2020	30	1

Sample output

A	B	C	Date	DifferenceDays	Flag	Output
a	p	N	5/31/2017	[Null]	[Null]
a	q	N	5/31/2020	1096	[Null]	-1
a	r	Y	6/30/2020	30	1	0
a	s	Y	3/31/2022	639	[Null]
b	t	N	10/31/2020	[Null]	[Null]	-1
b	u	Y	11/30/2020	30	1	0

[flying008 · Accepted solution]

Hi,@PB41091 

as your need ?