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
>