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MathGroup Archive 2005

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reducing the time of constructing a List

  • To: mathgroup at smc.vnet.net
  • Subject: [mg57533] reducing the time of constructing a List
  • From: marloo3 at mail15.com
  • Date: Tue, 31 May 2005 05:00:08 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

please, what is the best way to reduce the timing of the following lines, the 
source of data is:
dat = Table[Random[Integer, {0, 10}], {100000}];
and the purpose is to construct the List lst in the following way:
For[i = 1, i <= 100000,
      If [dat[[i]] == 1,
        lst = Join[lst, {1}], lst = Join[lst, {0}]]; i++]; // Timing

Out[]= {226.07 Second, Null}
on the P4 celeron 2 Ghz , memory 382 MB ram
thanks


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