Re: Sorting with Infinity
- To: mathgroup at smc.vnet.net
- Subject: [mg23520] Re: Sorting with Infinity
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Tue, 16 May 2000 22:29:52 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <8fqrpb$h5g@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
Sort[{-2, 1, 7, -Infinity, Infinity}, N[#1] < N[#2] &]
gives
{-\[Infinity], -2, 1, 7, \[Infinity]}
Regards
Jens
Jack Goldberg wrote:
>
> Hi group;
>
> I construct lists which may look like this
>
> {7,-2,-Infinity,Infinity,1}
>
> When this list is sorted by using Sort, I get
>
> {-2,1,7,-Infinity,Infinity}
>
> I would prefer, naturally,
>
> {-Infinity,-2,1,7,Infinity}
>
> This is easy to do if one doesn't care about elegance. Without
> spelling out the obvious details, here are a few kludges:
>
> (1) Replace Infinity by 10^15, Sort then switch back to Infinity.
> (2) Use Append and Prepend after Sort and deleting infinities.
> (3) RotateRight after Sort and switch signs on infinities
>
> Anyone got a "cute" solution say by using a sorting function or
> perhaps some arcane command unknown to mere mortals?
>
> Jack
>
>