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MathGroup Archive 2002

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Re: Import variable and data

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32706] Re: [mg32682] Import variable and data
  • From: BobHanlon at aol.com
  • Date: Thu, 7 Feb 2002 05:09:32 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 2/6/02 6:07:58 AM, mvdv at bigfoot.com writes:

>I'm having trouble with the following variable and data import:
>The import file is input.txt:
>
>a b c d
>1 23 45 678
>
>inputData=Import[input.txt,"Table"]
>{{a,b,c,d},{1,23,45,678}}
>
>This all works OK.
>Head[..]  indicates the a,b,c and d are strings, which is fine, because
>ToExpression[..] changes them to symbols.  What I'd like to do is use
>inputData to do the following:
>
>{a,b,c,d}={1,23,45,678}
>
>However, if I try
>
>ToExpression[ inputData[[1]] ] = inputData[[2]]
>
>I get an error:
>
>Set::write: Tag ToExpression in ToExpression[a] is Protected.
>
>If I then enter 'a' in Mathematica I do not get 1 returned!  No matter
>how I try I
>can't work it so that when I enter the symbol 'a' in Mathematica I get
>the value
>from inputData[[2]].
>

Attributes[Set]

{HoldFirst, Protected, SequenceHold}

The lhs must be evaluated

Evaluate[ToExpression[inputData[[1]]]]=inputData[[2]];


Bob Hanlon
Chantilly, VA  USA


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