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MathGroup Archive 1999

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Re: List Position

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15769] Re: [mg15740] List Position
  • From: Carl Woll <carlw at fermi.phys.washington.edu>
  • Date: Sun, 7 Feb 1999 02:03:50 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Harry,

The most straightforward solution is to use Position[], as in

Position[{{1},{1},{2},{8},{-3}}, a_ /; a<=0, 2, 1]

The syntax for Position is

Position[expr, pattern, levelspec, n]

where n tells mathematica to retrieve the first n positions which match
the pattern.

Carl Woll
Dept of Physics
U of Washington

On Fri, 5 Feb 1999, Harry flynn wrote:

> Can anyone tell me how I find the position in a list of the first value
> less than or equal to zero.
> For example, how can I get Mathematica to tell me that in the list
> {{1},{1},{2},{8},{-3}}
> that the first value of interest to me is position 5. Thanks in advance.
> Harry.
> 
> 



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