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List Operations

• To: mathgroup at smc.vnet.net
• Subject: [mg65681] List Operations
• From: "LectorZ" <lectorz at mail.ru>
• Date: Fri, 14 Apr 2006 04:32:05 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Hi guys,

My question:

mylist={{1,a, b},{1,a, b},{1,a,
b},{2,b,z},{2,b,z},{2,b,z},{2,b,z},....,{n,x,y},{n,x,y},{n,x,y},...{n,x,y}}

The sublists are of different length.

I need to calculate the product between the 2nd and 3rd element of
every sublist (e.g. a*b) and then add them up according to the 1st
element: sum of all products where the 1st element is 1, 2, ...n.

The result should be a list like that:
{{1,a*b+a*b+a*b},{2,b*z+b*z+b*z+b*z}, ...,{n, x*y+x*y+x*y+...+x*y}}

Thank you for your help.

LZ

• Follow-Ups:
  • Re: List Operations
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>