Re: reducing the time of constructing a List

*To*: mathgroup at smc.vnet.net*Subject*: [mg57576] Re: reducing the time of constructing a List*From*: "Mariusz Jankowski" <mjankowski at usm.maine.edu>*Date*: Wed, 1 Jun 2005 06:02:55 -0400 (EDT)*Organization*: University of Southern Maine*References*: <d7haeo$3pa$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

here is a simple and fast method: lst = Table[ If[ dat[[i]] == 1, 1, 0], {i, Length[dat]}] (Your timing should now be under 0.1 second) Mariusz >>> <marloo3 at mail15.com> 05/31/05 5:23 AM >>> 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