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