Software for pattern recognition in QSAR studies?

 Dear all,
 I am looking for a program that can apply standard pattern recognition
 techniques. Basically, I want to study a number of samples, each of
 which can be characterized by some properties. I would like to classify
 these samples into several groups based on these properties, and then
 derive a QSAR model for each group.
 So, I would like to try some popular software in this area for the
 clustering purpose. If you have any clue, please kindly let me know, and
 I will put back the summary shortly.
 Best regards,
 Renxiao Wang, Ph.D.
 Research Investigator
 Department of Internal Medicine, Hematology/Oncology Division
 University of Michigan Medical School
 Ann Arbor, MI 48109, U.S.A.
 Tel: (734) 764-2449; Fax: (734) 764-2532
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