Groups > comp.soft-sys.math.mathematica > #1769

Re: SortBy

From	Dana DeLouis <dana01@me.com>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Re: SortBy
Date	2011-04-17 23:15 +0000
Organization	Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID	<iofsak$s3j$1@smc.vnet.net> (permalink)

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> > 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

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Re: SortBy Dana DeLouis <dana01@me.com> - 2011-04-17 23:15 +0000

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