Re: reducing the time of constructing a List

*To*: mathgroup at smc.vnet.net*Subject*: [mg57600] Re: reducing the time of constructing a List*From*: "Peltio" <peltio at trilight.zone>*Date*: Wed, 1 Jun 2005 06:04:47 -0400 (EDT)*References*: <d7haeo$3pa$1@smc.vnet.net>*Reply-to*: "Peltio" <peltioNOSPAM at despammed.com.invalid>*Sender*: owner-wri-mathgroup at wolfram.com

someone wrote >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 > This is a list that turns every element not 1 into a zero. Create a function to do so f[1]=1; f[x_]=0; and then map it onto your original list lst = f /@ dat cheers, Peltio