FW: Czekanowski's coefficient - which is which.

[MANMEET SINGH]

I will try to verify other indices but I am sure Sorensens' Index is
different . It is
S(c)=2C/(A+B)
Manmeet Singh


On Tue, 29 Feb 2000, Jeremy J. Bruhl 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.
>
> Hi to everyone,
>
> I am reviewing a number of similarity/disimilarity (distance) coefficients often used in ecological data analysis. One problem I have come across is the numerous names under which some coefficients are known.
> One particular coefficient is Czekanowski's coefficient of similarity. From my reading, this particular index is used when quantitative (abundance) data is available and has the formula:
> S(c)=[2(sum(min(Xj,Yj)}]/(sum Xj + sum Yj)
> Yet, I have also come across another formula for this index which is used
> with binary data (presence/absence). The formula is
> S(c)*/(2a + b + c)
> (see Clifford H.T. and Stephenson W. 1975 " An introduction to numerical classification". Academic Press. Pp55)
> 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).
> Any help would be appreciated.
> Thank you in advance
> Eddy Cannella
> cannella at ozemail.com.au
>