MathGroup Archive 2001

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Sorting and Selecting in MultiLevel Lists?

  • To: mathgroup at
  • Subject: [mg31163] Sorting and Selecting in MultiLevel Lists?
  • From: aes <siegman at>
  • Date: Sun, 14 Oct 2001 04:11:58 -0400 (EDT)
  • Organization: Stanford University
  • Sender: owner-wri-mathgroup at

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?

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