ArrayFormula of Resetting Running Total in Google Sheets
Solution 1:
In addition, you could also try
=ArrayFormula(if(len(A:A),mmult(--transpose(if( (transpose(row(A:A))>=row(A:A))*(A:A=transpose(A:A)),B:B, 0)),row(A:A)^0),))
This should also work if the data is unsorted.
Solution 2:
If the table is always sorted on column A, you can just do:
=ARRAYFORMULA(SUMIF(ROW(B1:B6), "<="&ROW(B1:B6), B1:B6)-SUMIF(A1:A6, "<"&A1:A6, B1:B6))
If the table is not sorted, you can still do it with a vlookup:
=ARRAYFORMULA(SUMIF(ROW(B1:B6), "<="&ROW(B1:B6), B1:B6)-SUMIF(row(A1:A6), "<"&vlookup(A1:A6,{A1:A6,row(A1:A6)},2,false), B1:B6))
