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MathGroup Archive 2007

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Re: Iterate through a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76999] Re: [mg76886] Iterate through a list
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Thu, 31 May 2007 03:31:18 -0400 (EDT)
  • References: <1090841.1180516673633.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

v = {{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}};

v[[All, 1]]

{1, 1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 8, \
8, 8, 8, 8, 8, 8, 8, 8, 8}

or

First /@ v

{1, 1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 8, \
8, 8, 8, 8, 8, 8, 8, 8, 8}

Bobby

On Tue, 29 May 2007 04:02:03 -0500, Nick Hoffman <hoffmannick at gmail.com>=
  =

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!
>
>



-- =

DrMajorBob at bigfoot.com


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