Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!samsung!noose.ecn.purdue.edu!lips.ecn.purdue.edu!kavuri From: kavuri@lips.ecn.purdue.edu (Surya N Kavuri ) Newsgroups: comp.ai.neural-nets Subject: Re: Clustering Message-ID: <1991May21.213429.1672@noose.ecn.purdue.edu> Date: 21 May 91 21:34:29 GMT References: <1991May20.203008.27681@noose.ecn.purdue.edu> Sender: root@noose.ecn.purdue.edu (ECN System Management) Organization: Purdue University Engineering Computer Network Lines: 22 In article , greenba@gambia.crd.ge.com (ben a green) writes: > In article <1991May20.203008.27681@noose.ecn.purdue.edu> kavuri@lips.ecn.purdue.edu (Surya N Kavuri ) writes: > > Is there any reason why clustering is always(atleast what I > saw in books) unsupervised ? > > Clustering is a way to sort things into groups that share similarities. > If you already know the classes to which the things belong, what's the > point of trying to cluster them? > > Ben An obvious reason is the reduction in dimensionality of the problem. Another is the identification of the modes of a class so that the density can be approximated at each mode by a density function of known functional form (say, Gaussian). I have been told that there is such a thing as supervised clustering. An inexpensive clustering scheme is always a good preprocessing step. SURYA KAVURI (FIAT LUX)