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Re: Re: position of sequence of numbers in

  • To: mathgroup at smc.vnet.net
  • Subject: [mg107018] Re: [mg107005] Re: [mg106976] position of sequence of numbers in
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sun, 31 Jan 2010 08:18:38 -0500 (EST)
  • Reply-to: hanlonr at cox.net

This is wrong. I obviously didn't test this. Instead, use

myList = {3, 1, 2, 5, 3, 4, 6, 2, 8, 9, 3, 4}

{3,1,2,5,3,4,6,2,8,9,3,4}

Select[Position[myList, 3],
 MemberQ[Position[myList, 4] - 1, #] &]

{{5}, {11}}


Bob Hanlon


---- Bob Hanlon <hanlonr at cox.net> wrote: 

=============

Position[list, Sequence[3, 4]]


Bob Hanlon

---- 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




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