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MathGroup Archive 2011

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Multiple use of Set on lists

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119756] Multiple use of Set on lists
  • From: Jonathan Frazer <J.Frazer at sussex.ac.uk>
  • Date: Mon, 20 Jun 2011 19:38:06 -0400 (EDT)
  • References: <itm0of$143$1@smc.vnet.net> <201106201204.IAA07658@smc.vnet.net>

Hello,

I have a largish list of awkwardly "indexed variables", of the form cs = 
{c[1/2][-(1/2)][1/2][-(1/2)][-1], c[1/2][-(1/2)][1/2][1/2][-1]......etc....
....} which need to be assigned random values multiple times inside a Do loop. I was hoping I could generate a new list of random numbers each time then do something like

MapThread[Set, {cs, rands}]

Where "rands" would be the list of random numbers. I'm clearly misunderstanding how MapThread works though as this doesn't work. Rather than getting "c[1/2][-(1/2)][1/2][-(1/2)][-1]=new random number", instead "old random number=new random number" is what seems to be happening.

As a last resort I thought I would just clear the variables at the beginning of the do loop but you can't use Clear to do this and I don't see how you can apply "=." (Unset) over a list either.

Any suggestions?

Many thanks,

Jonny



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