Re: Sorting and Selecting in MultiLevel Lists?

*To*: mathgroup at smc.vnet.net*Subject*: [mg31175] Re: Sorting and Selecting in MultiLevel Lists?*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Tue, 16 Oct 2001 01:18:52 -0400 (EDT)*Organization*: Universitaet Leipzig*References*: <9qbi2c$2d7$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, since you compute x^2+y^2 twice in every comparsion it seems to be better to compute thist value one for every pair and remove it when you have sorted the pairs. Take[#, 2] & /@ Sort[Append[#, Dot[#, #]] & /@ myList, Last[#1] < Last[#2] &] Regards Jens aes wrote: > > Suppose I want to Sort, or Select from, a multilevel list, e.g. > > myList = { {x1,y1}, {x2,y2}, {x3,y3}, . . . } > > with a Sort or Select criterion that's some function of the xn and yn values > > For example, I can sort the above list on the value of x^2 + y^2 by using > > Sort[myList, (Take[#1, 1][[1]]^2 + Take[#1, 2][[1]]^2) < > (Take[#2, 1][[1]]^2 + Take[#2, 2][[1]]^2) &] > > Question: Is there an easier way to get at the "x" and "y" values associated > with the #1 and #2 arguments in Sort, or with the # argument in Select, than the > awkward Take[#,m][[n]] notation used here?