Re: [R] 1-Pearson's R Distance

From: William Revelle <>
Date: Thu, 27 Nov 2008 12:13:21 -0600

At 5:00 PM +0100 11/27/08, Claudia Beleites wrote:
>Hi Rodrigo,
>afaik, (1 - r_Pearson)/2 is used rather than 1 - r_Pearson. This gives a
>distance measure ranging between 0 and 1 rather than 0 and 2. But after all,
>dies does not change anything substantial.
>see e.g. Theodoridis & Koutroumbas: Pattern Recognition.
>I didn't know of the proxy package, but the calculation it straightforward
>(though a bit wasteful I suspect: first the whole matrix is produced, and
>as.dist cuts it down again to a triangular matrix):
>as.dist (0.5 - cor (t(x) / 2))
>Take care wheter you want to use x or t(x).
>HTH Claudia

 From the law of cosines, d = sqrt(2(1-r)) is a somewhat more appropriate transformation of a Pearson correlation to a distance.

Although this is monotonically related to the (1-r)/2, by taking the square root it will lead to somewhat different solutions in clustering.


William Revelle
Department of Psychology   
Northwestern University
Attend  ISSID/ARP:2009     

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Received on Thu 27 Nov 2008 - 18:15:45 GMT

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