[R] Similarity matrix
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Wed Apr 11 09:04:13 CEST 2001
On Tue, 10 Apr 2001, Frank E Harrell Jr wrote:
> I frequently use hclust on a similarity matrix. In R only a
> distance matrix is allowed. Is there a simple reliable
> transformation of a similarity matrix that will result
> in a distance matrix making hclust work the same as
> S-Plus with a similarity matrix? Venables & Ripley 3rd
We'd have to know how S-PLUS works!
> edition implies that a simple reversal of values
> will suffice.
Not quite. We say the scale is reversed, but not that it is linearly
reversed, because I don't know. Of course it only matters for
average-link clustering (in hclust).
The usual way to do this is to scale similarities to [0, 1] and take
D = sqrt(1-S) I believe, but I don't know why.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch
More information about the R-help