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Re: summing algorithm

To: s-news@lists.biostat.wustl.edu (S-NEWS)
Subject: Re: summing algorithm
From: sbackwards@comcast.net (SD Chasalow)
Date: Fri, 17 Feb 2006 16:19:28 +0000
Cc: rodmach@uclink.berkeley.edu
An algorithm for generating such partitions was published in JRSS C (Applied 
Statistics) in 1997:

@Article{Garcia-Perez:1997:DIA,
  author =       "M. A. Garcia-Perez",
  title =        "{AS 320}: Decomposing an integer {$N$} into all sets
                 of {$J$} positive integer summands by simulation of
                 dynamically varying nested {DO} loops",
  journal =      j-APPL-STAT,
  volume =       "46",
  number =       "4",
  pages =        "522--??",
  month =        "????",
  year =         "1997",
  CODEN =        "APSTAG",
  ISSN =         "0035-9254",
  bibdate =      "Sat Jan 2 15:12:05 MST 1999",
  acknowledgement = ack-nhfb,
}

This algorithm is quite similar to that implemented in function xsimplex in the 
combinat library section/package, although xsimplex solves a related but 
different problem.

You also can find pseudo-code for this problem in some combinatorics books such 
as "Combinatorial Algorithms" by Reingold, Nievergelt, and Deo.

Cheers,
Scott

Scott Chasalow
Statistical Genetics & Biomarkers
Bristol-Myers Squibb

> Dear users
> 
> Is there a general algorithm for finding all sets of say k +ve integers that 
> sum
> to S. For example, say I need all sets of 3 positve integers that sum to 6 : 
> (1,2,3), (1,1,4), (2,2,2).
>
> Thanks
>
> rhoderick 

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