Hi,
I have a table describing sort of ordered road segments and their associated weight. I would like to calculate weight deltas between two consecutive segments. Problem is to substract previous from current row and reuses result as input for the next row. I tried some windowing tests but was unsuccessful.
Input table :
road segment weight
1 1 80
1 2 5
1 3 3
2 1 75
2 2 8
2 3 12
2 4 3
The result should be a new delta column :
road segment weight delta
1 1 80 80 (80-0) first row
1 2 5 75 (80-5)
1 3 3 72 (75-3)
2 1 75 75 (75-0)
2 2 8 67 (75-8)
2 3 12 55 (67-12)
2 4 3 52 (55-3)
Thanks for any help,
By the way, thanks again to Andreas and Martin that unstucked my mind yesterday as I was searching for complicated solutions when a very simple one existed.
Have a good day (or good evening)
Olivier