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MathGroup Archive 2006

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Re: how to sum lists of unequal length?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg70443] Re: [mg70352] how to sum lists of unequal length?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 16 Oct 2006 02:35:58 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

sumLists[a_?VectorQ, b_?VectorQ] :=
    Module[{len = Max[Length /@ {a, b}]},
      PadRight[a, len] + PadRight[b, len]];

sumLists[{a1, a2, a3}, {b1, b2, b3, b4, b5}]

{a1+b1,a2+b2,a3+b3,b4,b5}


Bob Hanlon

---- Arkadiusz.Majka at gmail.com wrote: 
> Hi all,
> 
> I have lists of unknown and unequal lengths. I want to sum them, e.g
> 
> {a1,a2,a3}+{b1,b2,b3,b4,b5} and obtain result
> {a1+b1,a2+b2,a3+b3,b4,b5}. Simply filling by zeros of the shorter list
> is impossible because I have no idea how many zeros I have to pad.
> 
> Please, help
> 
> Arek
> 

--

Bob Hanlon
hanlonr at cox.net



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