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Re: Subsetting indexed variable?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg36041] Re: [mg36028] Subsetting indexed variable?
  • From: BobHanlon at aol.com
  • Date: Wed, 14 Aug 2002 05:35:09 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 8/13/02 6:41:17 AM, gjr2008 at columbia.edu writes:

>I cannot seem to work out how to extract a subset of information from an
>indexed variable (without generating a full list/matrix first).
>
>For example, suppose I define:
>
>b[1,3] = 3
>b[2,3] = 7
>b[2,4] = 5
>
>And I then want to get the list of all DEFINED values of b[2,_], i.e.,
>the
>result should be {7,5}

Cases[DownValues[b], b[2, _], Infinity]


Bob Hanlon
Chantilly, VA  USA


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