Re: SortBy
- To: mathgroup at smc.vnet.net
- Subject: [mg118251] Re: SortBy
- From: Dana DeLouis <dana01 at me.com>
- Date: Sun, 17 Apr 2011 19:15:58 -0400 (EDT)
> > KS = {{300, 48, 2}, {500, 23, 5}, {120, 55, 7}, {40, 32, 1}};
> > I want to sort it by second element.
> > But if I want to use SortBy, how to do that?
>
> While there are functions First and Last, there is no Second and Third,
> but maybe that's an inexpensive possibility to increase the number of
> functions in the next version even more :-).
>
> SortBy[KS, #[[2]] &]
I was just playing around with this idea. There's probably a better
way if you wanted to go this route.
(* Skip the reserve word First, and carry out as far as you want *)
var={Null, Second, Third, Forth, Fifth, Sixth, Seventh};
MapIndexed[Function[{n,v},n := #1[[v]] & ],var]//Quiet;
t=Partition[RandomSample[Range@12],4]
{{2,10,7,5},{3,4,12,6},{9,8,11,1}}
SortBy[t,First]
{{2,10,7,5},{3,4,12,6},{9,8,11,1}}
SortBy[t,Second]
{{3,4,12,6},{9,8,11,1},{2,10,7,5}}
SortBy[t,Third]
{{2,10,7,5},{9,8,11,1},{3,4,12,6}}
SortBy[t,Forth]
{{9,8,11,1},{2,10,7,5},{3,4,12,6}}
= = = = =
Dana
Mac, Ver 8