Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2011

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

Search the Archive

Re: Sort on vector component

  • To: mathgroup at smc.vnet.net
  • Subject: [mg122014] Re: Sort on vector component
  • From: "Chris Degnen" <degnen at cwgsy.net>
  • Date: Sun, 9 Oct 2011 03:51:40 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <j6q647$p1v$1@smc.vnet.net>

To sort by the last position use SortBy[u, Last]
and for other positions, say the third, use Ordering:
u[[Ordering[u[[All, 3]]]]]


Dr. Wolfgang Hintze wrote:
>
> Given a list
> 
> u = {{2, 12, 7, 21}, {2, 48, 47, 97}, {4, 42, 41, 87},
> {6, 8, 1, 15}, {6, 12, 9, 27}}
> 
> How can I sort it with respect to a given index position i=(1, ..., 4)?
> 
> For i=1 it is simply Sort, for the last one I could use
> 
> In[75]:=
> Reverse /@ Sort[Reverse /@ u]
> Out[75]=
> {{6, 8, 1, 15}, {2, 12, 7, 21}, {6, 12, 9, 27},
> {4, 42, 41, 87}, {2, 48, 47, 97}}
> 
> I don't want to go in the details of defining lexicographical order but 
> just obtain a sorting as described above.
> 
> Any ideas?
> 
> Thanks in advance.
> 
> Wolfgang
> 
>




  • Prev by Date: general formula for differentiating a spherical bessel function of
  • Next by Date: Re: "Esoteric of the week"
  • Previous by thread: Re: Sort on vector component
  • Next by thread: Re: Sort on vector component