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st: RE: clustering question


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: clustering question
Date   Thu, 3 Dec 2009 20:27:53 -0000

I can't see that the request makes any sense. 

You might as well say "Last year, I calculated averages for the client,
and the client was happy. Now the client has new data and wants new
averages except that the old averages should be used in constructing
them." You must choose: old or new or both. 

All you can do is apply the same method to the new data, and that takes
no cognisance of the old data. In fact, the new clustering might be some
sort of check on the old, except that it may be too late for the client.


There are variants on this such as combining old and new datasets. 

It could be different, although not necessarily a better idea, for a
method such as -pca-, which leaves pertinent results in its wake. 

Nick 
n.j.cox@durham.ac.uk 

Data Analytics Corp.

Last year, I developed a simple three-cluster solution for a client 
based on survey data using the following:

    cluster wardslinkage q16r6 q17r5 q17r7 q17aa1r1 q17ab1r1 q17ab1r7 
q17ab1r9 vytldl, measure(Gower) name(clus01);
    cluster dendrogram clus01, xlabel(, angle(90) labsize(*0.75)) 
cutnumber(30) title("Wave 17 Cluster Analysis")
        note("Notes:" "Based on Wards linkage" "062209_1 cluster.do");
    cluster gen g = group(3), name(clus01);

The client was happy.  Now this year, the client redid the survey but 
wants to use the same cluster solution as last year, only with the data 
from the new survey.  How do I use the previous solution with new data?

I have both Stata 10 and 11 for Windows.


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