Canberra distance

<Bill.Venables <at> csiro.au> writes:

That is interesting.  The first of these, namely

sum(|x_i - y_i|) / sum(x_i + y_i)

is now better known in ecology as the Bray-Curtis distance.  Even more

interesting is the typo in Henry &

Stevens "A Primer of Ecology in R" where the Bray Curtis distance formula is

actually the Canberra

distance  (Eq. 10.2 p. 289).  There seems to be a certain slipperiness of

definition in this field.

Thank you for bringing to my attention the similarity of the Canberra and
Bray-Curtis quantitative indices. Bray-Curtis dissimilarity can also, of course,
be defined as 

1 - 2w/(a+b) 

where w is sum of the minimum of each relevant pair of values, and a and b are
the totals for sites a and b, respectively. These definitions appear to yield
similar results, and to better reflect the original work by Bray and Curtis, I
should probably define their distance as they did!

Cheers,

Martin Henry Hoffman Stevens (a.k.a. Hank)

What surprises me most is why ecologists still cling to this way of doing

things,  It is one of the few places I

know of where the analysis is justified purely heuristically and not from any

kind of explicit model for

the ecological processes under study.

Bill Venables.

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