Re: Re: position of sequence of numbers in list

*To*: mathgroup at smc.vnet.net*Subject*: [mg107012] Re: [mg106993] Re: [mg106976] position of sequence of numbers in list*From*: Leonid Shifrin <lshifr at gmail.com>*Date*: Sun, 31 Jan 2010 07:53:37 -0500 (EST)*References*: <201001301212.HAA25132@smc.vnet.net>

Patrick, Bob, Please educate me if I am misunderstanding, but Position is not SequenceHold and therefore, your constructs don't seem to work for me. They seem to work only because you provided length - 2 or length- 3 sequences (try length-4 and I am getting en error for v7), which Position interprets as 2 or 3 additional arguments. Thus, Position[list, Sequence[11, 12, 13]] is equivalent to Position[list, 11,12,13], which means: find position of element <11> in the first 12 levels of expression (<list>), stopping with at most 13 results. By accident (or luck), this gives correct result on the toy example that you have. The same situation with Bob's example Position[list, Sequence[3, 4]]. Or is this an extension of v.7.1, that I am not aware of? Regards, Leonid On Sun, Jan 31, 2010 at 2:55 AM, Patrick Scheibe < pscheibe at trm.uni-leipzig.de> wrote: > Hi, > > I assume the only thing you miss is how to express a "sequence of > numbers"? Just use Sequence[] :-) > > list=Range[20]; > Position[list, Sequence[11, 12, 13]] > > Cheers > Patrick > > On Sat, 2010-01-30 at 07:12 -0500, JB 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>