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MathGroup Archive 2005

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Re: Position function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55582] Re: Position function
  • From: yasdfer at yahoo.com
  • Date: Wed, 30 Mar 2005 03:21:26 -0500 (EST)
  • References: <d2b4q9$77c$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

konstantpi at mail15.com wrote:
> suppose i have a List:
> a={{1,3,1,2,1},{5,6,1,1,3,1}}
> how i could know the positions of "1" in every sublist , i could use
Position[a
> [[1]],1] and Position[a[[2]],1]
> but i want a one formula to give me {{1,3,5},{3,4,6}}
>

Flatten[Position[#,1]]& /@ a

> the second question:
> using Position[a,1] will give:
> {{1, 1}, {1, 3}, {1, 5}, {2, 3}, {2, 4}, {2, 6}}
> in general how to extract only the second item from every sublist so
the output
> will be;
> {1,3,5,3,4,6}

Transpose[Position[a,1]][[2]]

> thanks
> konst.


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