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Hi, suppose I have a simple sorted vector like this: a <- c(2,3,3,5,6,8,8,9,15, 25, 34,36,36,38,41,43,44,44,46); Is there a function in R, I can use to discover that from index 8 to index 11 the values are changing significantly? The function should return a value pointing to one of the indices 8, 9, 10 or 11. Any of them would be fine. The difficulty is that there may be no big gap. I

Hi, my problem is as follows: I have a matrix of two rows like this: 2 2 3 4 4 4 5 5 6 1 1 2 1 3 3 2 1 1 Can I apply something like "group by" in sql? What I want to achieve is the some of second row for each unique entry of first row: 2 -> 2 (=1+1) 3 -> 2 4 -> 7 (=1+3+3) 5 -> 3 (=2+1) 6 -> 1 Thanks!! Henning