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MathGroup Archive 2006

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Re: finding the position of a pattern in list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg64634] Re: finding the position of a pattern in list
  • From: "Scout" <Scout at nodomain.com>
  • Date: Fri, 24 Feb 2006 00:19:05 -0500 (EST)
  • References: <dtjjcv$de7$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"Gang Ma" <contactmagang at gmail.com>
> Hi,
> I am working on a program to do the following: My data is a list of 0
> and 1. For example, {0,0,1,1,1,0,0,1,1,1,0}. I want to find the
> positions of all the pattern of {0,1}.  In my previous example, the
> first {0,1} is at 2 and and the second {0,1} appears at 7. I can
> write a loop to do this, but I have several thousands such lists,
> the computation will be time consuming using loop.
>
> My question is whether it is possible to use the pattern match to do
> this quickly.  If not for the list, do I need to convert the list to
> string then use some pattern match for string?  Thank you very much.
>
> regards,
>
> Gang Ma
>
>
>
Hi,
I think a simple way to achieve that is:

    In[1]:= data={0,0,1,1,1,0,0,1,1,1,0} ;

    In[2]:= Position[Partition[data, 2, 1], {0, 1}]
    Out[2]= {{2},{7}}

    In[3]:= Flatten[%]
    Out[3]= {2,7}

Regards,
    ~Scout~


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