Re: reducing the time of constructing a List
- To: mathgroup at smc.vnet.net
- Subject: [mg57562] Re: [mg57533] reducing the time of constructing a List
- From: "David Park" <djmp at earthlink.net>
- Date: Wed, 1 Jun 2005 06:02:00 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
You are just replacing non-unit entries in dat by 0. Use functional
programming and forget For statements.
dat = Table[Random[Integer, {0, 10}], {100000}];
lst = If[# == 1, 1, 0] & /@ dat; // Timing
{0.05 Second, Null}
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
From: marloo3 at mail15.com [mailto:marloo3 at mail15.com]
To: mathgroup at smc.vnet.net
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