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MathGroup Archive 2007

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Re: Iterate through a list help

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77259] Re: Iterate through a list help
  • From: dh <dh at metrohm.ch>
  • Date: Wed, 6 Jun 2007 07:00:55 -0400 (EDT)
  • References: <f43gfu$2cq$1@smc.vnet.net>


Hi Nick,

by myList[[All,1]] you get all the first numbers.

hope this helps, Daniel



Nick wrote:

> Hello! I'm (somewhat) new to Mathematica and I  need help to iterating

> through a list and counting the occurrence of a number.

> 

> My list looks like:

> 

> {{1,0},{1,1},{2,x+x^2+x^4},{2,1+x+x^2+x^4},{4,x+x^2},{4,1+x+x^2},{4,x

> +x^4},{4,1+x+x^4},

> {4,x^2+x^4},{4,1+x^2+x^4},{4,x^3+x^4},{4,1+x^3+x^4},{4,x+x^2+x^3+x^4},

> {4,1+x+x^2+x^3+x^4},

> {5,x+x^3},{5,1+x+x^3},{5,x^2+x^3},{5,1+x^2+x^3},{5,x+x^3+x^4},{5,1+x

> +x^3+x^4},{5,x^2+x^3+x^4},

> {5,1+x^2+x^3+x^4},{8,x},{8,x^2},{8,x^3},{8,x^4},{8,1+x},{8,1+x^2},

> {8,1+x^3},{8,x+x^2+x^3},{8,1+x+x^2+x^3},{8,1+x^4}}

> 

> The number that I would need to keep track of is the first in each

> sub-

> list.

> 

> So for the first couple {{1,0},{1,1},{2,x+x^2+x^4},{2,1+x+x^2+x^4},

> {4,x

> +x^2},........

> 

> I would need to keep track of 1,1,2,2,4........

> 

> It will not always be 1,2,4,5,8's.  The numbers may be completely

> different on each pass.  Each sublist may be composed of more items

> but the number that I need to keep track of will always be the 1st in

> the sub-list.  Any help or suggestions that you can give me will be

> greatly appreciated.  Thanks so much!

> 

> 




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