From tjsm at pml.ac.uk  Fri Jul 15 10:11:22 2011
From: tjsm at pml.ac.uk (Tim Smyth)
Date: Fri, 15 Jul 2011 01:11:22 -0700 (PDT)
Subject: [Rd] fuzzy c-means algorithm in e1071
Message-ID: <1310717482041-3669374.post@n4.nabble.com>

I was wondering if it was possible to add an extra option to the cmeans
function please?  In a recent paper by Moore et al.,(2009) they state:

"The fuzzy membership function is: 1 - F(Z2), where Z2 is a squared
Mahalanobis distance and F is a cumulative chi-square distribution.  The
Mahalanobis distance is the multivariate equivalent of the standardised
random variable Z = (X - M)/S, which is the distance of the univariate
random variable X from its mean M normalised by the standard deviation S. 
In other words, the Mahalanobis distance is a weighted form of the
Euclidean, and is preferable because it incorporates the shape of the the
distribution of points around the cluster centre (i.e., the geometric shape
of the point cloud expressed in terms of variance). The fuzzy membership
ranges from 0 to 1 ..."

so as well as having a dist = "euclidean" option, would it be possible to
have a dist = "mahalanobis" option please?  I realise that this is quite an
ask - you could even point me in the right direction of where to start
editing code and getting it compiled on my own machine.

Tim Smyth

ref: T.S. Moore et al. Remote Sensing of Environment 113 (2009) 2424-2430 

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[Rd] fuzzy c-means algorithm in e1071
Tim Smyth