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MathGroup Archive 2005

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Re: Can't assign value to symbols

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58420] Re: Can't assign value to symbols
  • From: dh <dh at metrohm.ch>
  • Date: Sat, 2 Jul 2005 04:06:16 -0400 (EDT)
  • References: <da2mpq$93f$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Lee,
"Set" has the Attribute HoldFirst. Therefore, if you say
parameters[[1]] = parameters[[2]]
parameters[[1]] will not be evaluated and you are assigning to the array 
and not to a,b,c. If have to tell "Set" to evaluate its first argument by:
Evaluate[parameters[[1]]] = parameters[[2]]

sincerely, Daniel

Lee Newman wrote:
> Hello,
> 
> Situation:  I have a table that contains parameters and sets of values 
> that I want to assign to the parameters for the purposes of running a 
> simulation.
> - parameters = {{a,b,c},{1,2,3},{4,5,6},{7,8,9}}
> - want to assign values in a given row to the symbols listed in the 
> first row.
> - tried using:  MapThread[  #1 = #2 &, {parameters[[1]], parameters[[3]]} ]
> - fails with error  "Tag Slot in #1 is Protected"
> - tried adding Unprotect[#1] and a variety of other attemps, but can't 
> get it to work.
> 
> Anyone know how might accomplish this?
> 
> Thanks,
> Lee
> 
> 


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