MathGroup Archive 2002

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List processing

  • To: mathgroup at
  • Subject: [mg37196] List processing
  • From: John Leary <leary at>
  • Date: Wed, 16 Oct 2002 14:25:56 -0400 (EDT)
  • Sender: owner-wri-mathgroup at


This problem can be solved by conventional programming, but I wonder if 
there is an elegant Mathematica solution ?

A list contains pairs of values, with each pair representing the lower and 
upper edge of a sub-range.  Some of the sub-ranges partially overlap, some 
fully overlap, others don't overlap at all.  The problem is to produce a 
second list that contains the overall upper and lower edges of the 
overlapping sub-ranges.

A simple example :  {{100,200},{150,250},{120,270},{300,400}}  would result 
in {{100,270},{300,400}}.

In the real case, the input list has several hundred elements and the 
output list typically has five elements.

I have a working solution based on loops, but there must be a more elegant 
one.  I would be very grateful for any suggestions.

Best regards

John Leary

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