FW: Czekanowski's coefficient - which is which.

[Buz Wilson]

At 11:25 29/02/00 +1100, you wrote:
>-----Original Message-----
>From:   Eddy Cannella [SMTP:cannella at ozemail.com.au]
>Sent:   Thursday, May 28, 1998 5:04 PM
>To:     ESA at dwe.csiro.au
>Subject:        Czekanowski's coefficient - which is which.
>One particular coefficient is Czekanowski's coefficient of similarity.
>From my reading, this particular index is used when quantitative
(abundance) data is
...snip
>This formula is the same as that for Sorensons index on similarity.
>Would anyone out ther know whether this is an error or if the index was
>developed for both types of data (or is it an error on my part).

Your answer is in the documents to Eugene Gallagher's COMPAH96, available
at http://www.es.umb.edu/edgwebp.htm .  He has a section on equivalencies
of indices.  Here is an excerpt from the introduction to this section:

"Ecologists often use different names to describe the same index.  For
example, Czekanowski's binary, Sorensen's index, and the Dice index are
synonyms (Clifford & Stephenson 1975, p. 55).  Sometimes, ecologists call
different similarity indices by the same name.  For example, COMPAH's %
similarity (SIMOPT=9) is not the same as Pielou's (1984) percentage
similarity (SIMOPT=6).  Pielou's percentage similarity is known by several
synonyms: Czekanowski's quantitative index, Sorensen's quantitative index
(Magurran 1988, p. 95), and COMPAH's Bray-Curtis similarity index
(SIMOPT=6). "  [Table follows]

This section on indices is the one of the most informative treatments that
I have come across. Gallagher goes on to develop other new indices. I post
this to the list in case others don't know about this useful software and
documentation.

Cheers,

Buz Wilson
Australian Museum