Re: Sorting 3 points

*To*: mathgroup at smc.vnet.net*Subject*: [mg87980] Re: Sorting 3 points*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Mon, 21 Apr 2008 06:40:07 -0400 (EDT)*Organization*: University of Bergen*References*: <fuhfa6$ibk$1@smc.vnet.net>

carlos at colorado.edu wrote: > Simple question, but documentation is no help. > I have three coordinate triplets: > > P1={x1,y1,z1} P2={x2,y2,z2} P3={x3,y3,z3} > > where all entries are numeric. I wont to sort them into > > P1s={xs1,ys1,zs1} P2s={xs2,ys2,zs2} P3s={xs3,ys3,zs3} > > so that zs3>=zs2>=zs1, with one command > > {P1s,P2s,P3s}=Sort[{P1,P2,P3}, Ordering Function] > > Is that possible and if so, which Ordering Function > should be used? Thanks. Well, this is pretty simple if you read what an ordering function is ... Sort[list, Last[#1] < Last[#2] &] (Or if you have Mathematica 6, just use SortBy[list, Last]) Perhaps the missing piece was constructing anonymous functions? Read the doc page of Function for an explanation (#1, #2 are the first and second arguments of the function).