Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

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





  • Prev by Date: Re: opposite of partition
  • Next by Date: Re: List searching
  • Previous by thread: Re: reducing the time of constructing a List
  • Next by thread: Re: reducing the time of constructing a List