Re: reducing the time of constructing a List
- To: mathgroup at smc.vnet.net
- Subject: [mg57594] Re: [mg57533] reducing the time of constructing a List
- From: DrBob <drbob at bigfoot.com>
- Date: Wed, 1 Jun 2005 06:04:30 -0400 (EDT)
- References: <200505310900.FAA03434@smc.vnet.net>
- Reply-to: drbob at bigfoot.com
- Sender: owner-wri-mathgroup at wolfram.com
lst = dat /. x_Integer /; x â? 1 -> 0;
or
lst = dat /. {1 -> 1, x_Integer -> 0};
or
lst = Boole /@ Thread[dat == 1];
Bobby
On Tue, 31 May 2005 05:00:08 -0400 (EDT), <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
>
>
>
>
--
DrBob at bigfoot.com