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Date:         Mon, 26 Sep 2005 09:55:47 +1000
Reply-To:     Frank Milthorpe <>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Frank Milthorpe <>
Subject:      Re: 2nd Attempt: Grouping Zip Codes  - Integer programing may be
              the solution
Content-Type: text/plain; charset=US-ASCII


I am working though a backlog of email messages.

Can you provide some information on the number of zip codes in your dataset? If this a smallish number, say 100 you can probably get close to the minimum of sets "manually" by using a map and / or possibly a Geographic Information System. If you start at the zip codes at the extremities and group all regions within 10 minutes this will reduce the size of the problem. You could keep working through the problem.

Automated solutions are much better, especially if you decide the cut-off interval should be 15 minutes, rather than 10 minutes. To be sure that you are using the minimum number of groups sounds like an integer programming problem. I am sure that there are packages out there. I suspect that the cost of them may be comparable to SPSS. This is not an area that I have not been involved in since my undergraduate days. Is there anyone on the list who is aware of IP packages?



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Frank Milthorpe Senior Manager, Transport Modelling Transport and Population Data Centre Department of Planning Direct: (02) 9206 8609 Phone: (02) 9206 8611 Fax: (02) 9206 8691 Street: Level 7, Tower 2, 1 Lawson Square, Redfern NSW 2016 Mail: GPO Box 39, Sydney NSW 2001 Email: Web:

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