trending growth, next increment

Is there a way to find the trending growth (next increment) difference between a defined list of values ie

1 , 2, 3, 4, 5  -- the next increment would be 1
5,4,3,2,1   -- the next increment would be -1
2,4,6,8,10 -- the next increment  would be 2
20,15,25,10,30  -- the next increment would be 10

I dont want to subtract base values, so if the base value were lower than the previous value, the lower value would re establish the counter.

I would use to get trending growth of tablespaces, in this example over a 5 month period

Thanks
Bob

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