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August 2006

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Subject:
From:
Art Kendall <[log in to unmask]>
Reply To:
Classification, clustering, and phylogeny estimation
Date:
Mon, 14 Aug 2006 11:57:20 -0400
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It is some time since I used version 12,  but the hierarchical
clustering part has been around for since the  70's.
If you used the SAVE specification, you should have a new variable that
indicates for each case to which cluster it is assigned. say you called
it  Kluster3 and the variables to base the clustering on Var01 to Var12.


to get the centroids
(I'm not sure how you would have interpreted the cluster meanings
without using DISCRIMINANT or means already.)
discriminant  groups= kluster3 (1,3)/  variables = var01 to var12 . . ..

or
means tables= var01 to var12 by kluster3 /cells= count means . . . .

once you type the above command into a syntax window, highlight (select)
the procedure name with you mouse and click the syntax button to see
other possibilities for the procedure.

In DFA, I recommend closely examining the probabilities of assignment to
each cluster for each case, and the probability that a member of a
cluster would be as far away from the centroid as this particular case
is. This is a very old but very useful aid in interpreting a clustering.
The classification phase of DFA should provide insight into the
reliability of the cluster assignments.

The GUI in SPSS is very useful for the first draft of your syntax.
Simply exit the menus via the "paste" button.  This shows you the syntax
that will do what you specified in the menu.  As you look at your
results, and as you develop your approach you can simply edit the pasted
syntax.

To get your means into a .sav file.  There are more automated ways to
get the centroids into kmeans, but this is straightforward.
open a new data file
label the variables  kluster3 and var01 ... var12.
key in the centroids.
save the file.



You might also want to consider applying the TWOSTEP procedure.
It will produce AIC and BIC to check on the number of clusters to retain.

Art Kendall
Social Research Consultants


Aaron Eakman wrote:

>I am using SPSS 12 for my clustering procedures.  I started with
>heirarchical clustering using Wards method with squared euclidean
>distance.  I have identified a three cluster solution as the best option
>from a possible range of 2-4 that I established a priori.
>
>Here is my problem, I want to next run a K-means clustering procedure.
>More specifically, I want to use the centroids of the three clusters from
>my heirarchical procedure as "seed" or starting values for the K-means
>clustering procedure.  Unfortunately, SPSS does not generate this output
>from the heirarchical procedure.  And I do not know 1) how to generate
>cluster centroids from the cluster assignment information provided by SPSS
>heirarchical procedure, and 2) even if I did, I do not know how
>to generate an SPSS.sav file with that information for use by the K-means
>approach.  A further problem, I am a point and clicker and not savvy with
>command syntax; I AM WILLING TO LEARN IF IT CAN GET ME OUT OF MY MESS!!
>
>Any persons that are SPSS  - Cluster Analysis savvy, or know others that
>might lend a hand would be met with gratitude for any assistance.
>
>Take care,
>
>Aaron Eakman
>
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