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Date:         Wed, 24 Nov 1999 00:48:47 -0600
Reply-To:     "Nichols, David" <nichols@SPSS.COM>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "Nichols, David" <nichols@SPSS.COM>
Subject:      Re: Cluster Analysis

The only way that the order of cases can affect the results from CLUSTER is when you have tied distances. When the smallest distances between existing clusters (which are just cases at the beginning) are equal for two or more pairs, then the order can affect the results in that an arbitrary decision is made in terms of which pair to join. If I remember correctly, the search and replace algorithm that goes through the matrix replaces the marked minimum only if the new one is smaller, so in the case of ties, the first pair will be the one that gets joined.

David Nichols Principal Support Statistician and Manager of Statistical Support SPSS Inc.

> -----Original Message----- > From: Felix Brosius [SMTP:FelixBrosius@CSI.COM] > Sent: Sunday, November 23, 1997 3:48 AM > To: SPSSX-L@LISTSERV.UGA.EDU > Subject: [SPSSX-L] Cluster Analysis > > Dear Listmembers, > > under which circumstances/options does the order of the cases in the data > file have an influence on the results of an hierarchical cluster analysis, > especially in the context of the Ward-Method? > > Many thanks in advance > felix brosius

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