Re: Extracting information from lists

*To*: mathgroup at smc.vnet.net*Subject*: [mg63425] Re: Extracting information from lists*From*: "Borut Levart" <BoLe79 at gmail.com>*Date*: Sat, 31 Dec 2005 06:40:23 -0500 (EST)*References*: <dojefh$fmb$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Perhaps I don't fully comprehend your question, so I guess your problem is to find the position of start of ALL the runs. So it could be a run of 1's, or 3's, and you should be able to locate their starting positions. If that is so, I would do it like this: whereRuns[l_] := Position[ Replace[ Split[l], e_List?(Length[#] = 2 &) :> Prepend[Rest[e], xxx], 2] // Flatten, xxx] // Flatten The function locates the runs, it replaces their first element by xxx, and returns the positions of that xxx's. In:= where[lst] Out= {6,10,16} I didn't turn your 4th element, 6, into 1, as David Park did, so I don't get the desired result, but I also think your question is not in exact consistency with your result. Bye, Borut