Re: position of sequence of numbers in list

*To*: mathgroup at smc.vnet.net*Subject*: [mg106996] Re: [mg106976] position of sequence of numbers in list*From*: Leonid Shifrin <lshifr at gmail.com>*Date*: Sun, 31 Jan 2010 05:56:21 -0500 (EST)*References*: <201001301212.HAA25132@smc.vnet.net>

Well, Sorry for so many posts - apparently I did not include the code for <myPosition> function mentioned in my second post, while inluded the timings for it. Here it is: myPosition = Compile[{{lst,_Integer,2},{target,_Integer,1},{nresults,_Integer}}, Module[{i=1,len = Length[lst],positions = Table[0,{If[nresults!=-1,nresults,Length[lst]]}],pctr=0, lcnresults = If[nresults!=-1,nresults,Length[lst]]}, While[i<=len&&pctr<lcnresults, If[lst[[i++]]==target,positions[[++pctr]]=i-1]]; Take[positions,pctr]]] Regards, Leonid On Sat, Jan 30, 2010 at 4:12 AM, JB <jkerrb at gmail.com> wrote: > Hi, > > What is the most efficient way to find the position of the beginning > of a sequence of numbers from a list? > > I found a couple of ways: > > find 3,4 in list={1,2,3,4,5}; > > 1. pos=Intersection[Position[list,3],(Position[list,4])+1] > > 2. pos=Position[Partition[list,2,1],{3,4}] > > Are there other ways to do this? > What is the best way when dealing with large lists? > > Thanks, > JB > >

**References**:**position of sequence of numbers in list***From:*JB <jkerrb@gmail.com>