Re: reducing the time of constructing a List

*To*: mathgroup at smc.vnet.net*Subject*: [mg57556] Re: reducing the time of constructing a List*From*: dh <dh at metrohm.ch>*Date*: Wed, 1 Jun 2005 06:01:42 -0400 (EDT)*References*: <d7haeo$3pa$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, try replacing every elemnt different from 1 by zero: dat /. x_Integer -> 0 /; x != 1 sincerely, Daniel marloo3 at mail15.com wrote: > 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 >