Re: Mathematica 6.0 easier for me ... (small review)

*To*: mathgroup at smc.vnet.net*Subject*: [mg76556] Re: [mg76457] Mathematica 6.0 easier for me ... (small review)*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Thu, 24 May 2007 05:53:53 -0400 (EDT)*References*: <200705230859.EAA23180@smc.vnet.net>

On 23 May 2007, at 17:59, Paul at desinc.com wrote: > If I have > lis={{1,10},{2,10},...{9,10},{11,20},{12,20}...{19,20} > > How do I use functional and/or rule to determine where the second > number (lis[[i,2]]) jumped from 10 to 20 to 30 and save the pair. > Assuming there was noise, I only want to store the first 10->20, then > look for 20->30 and so on. So in time, I want my search to change as > I progress through the list. Any input appreciated! I am not quite sure if I really understand what you wish to do. But if what I think is correct, then it seems easy to do it using rule based programming: FirstJump[lis_, n_, m_] := Flatten[({ lis} /. {___, {x_, n}, {y_, m}, ___} :> Position[lis, {x, n}])] For example: ls={{1,10},{2,10},{9,10},{11,20},{12,20},{19,20},{20,30}}; FirstJump[ls,10,20] {3} FirstJump[ls,20,30] {6} The above assumes that all the pairs in your list are distinct. If they are not, then something more complicated is needed, e.g.: Clear[FirstJump] FirstJump[lis_, n_, m_] := Position[Flatten[({lis} /. {a___, {x_, n}, { y_, m}, b___} :> {a, $1, $2, b}), 1], $1, 1] ls = {{1,10}, {2, 10}, {9, 10}, {9, 10}, {11, 20}, {12, 20}, {19, 20}, {20, 30}}; FirstJump[ls, 10, 20] {{4}} Andrzej Kozlowski

**References**:**Mathematica 6.0 easier for me ... (small review)***From:*Paul@desinc.com