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MathGroup Archive 2005

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Re: Clear subscripted variables

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58290] Re: [mg58276] Clear subscripted variables
  • From: Pratik Desai <pdesai1 at umbc.edu>
  • Date: Sun, 26 Jun 2005 01:33:52 -0400 (EDT)
  • References: <200506250556.BAA12738@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Mukhtar Bekkali wrote:

>Here is the code (x\_i stands for x subscript i):
>
>Table[{Print[x\_i = i]; Clear[x]; Remove[x]; Unset[x]; Print[x\_i]},
>{i, 1, 2}]
>
>I expected that x\_i is cleared at the end of the loop but it isn't
>
>If I insert Clear[Subscript] in the loop then it is cleared, but not
>desirable since it clears all variables with subscripts.
>
>What command shall I use to clear specific subscripted variables?
>
>Mukhtar Bekkali
>
>  
>
Hi,
Here is what I think the problem is
Why is x equal to x\_i?
Even if it is, how can mathematica know it

I think what you can try is
Table[Subscript[x, i] = 1, {i, 1, 2}]
(*Table[Unset[Subscript[x, i]], {i, 1, 2}]
Table[Subscript[x, i], {i, 1, 2}]*)

You can uncomment the unset table to clear the variables, or better yet 
write a module to do it (i.e Unset the subscipted variables)

Here is a rough version of the same

unsetmod[x_, list_] := Module[{list1}, list1 =
   list; Table[Unset[Subscript[x, list1[[s]]]], {s, 1, Length[list]}]]

Table[Subscript[x, i] = 1, {i, 1, 5}]
(*unsetmod[x, Range[2]]*)
Table[Subscript[x, i], {i, 1, 5}]

Best regards
Pratik

-- 
Pratik Desai
Graduate Student
UMBC
Department of Mechanical Engineering
Phone: 410 455 8134



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