In article 4947 at dflora.cuug.ab.ca, peter at dflora.com (Peter D. Wilson)
>Posting for a friend:
>>I have been asked to trace some software which performs
>"Trended Correspondence Analysis". It is to be used in botany and is
>believed to have been created by a botanist. Any help would be
>peter d. wilson
>email: peter at dflora.com (NeXTMail OK)
>Voice: (403) 283-9743 Fax: (403) 283-0036
> Independent NextStep Developer
The technique is "Detrended Correspondence Analysis," where detrending
refers to subtracting a smooth non-linear dependence among the axes,
characteristic of correspondence analysis solutions for data where
there is lots of species turnover amoung the sampling locations. The
most popular computer code for calculating the solution is a Fortran
program called DECORANA, by Mark Hill. Along with various public and
'at cost' implementations, there are supported commercial versions.
Most owe something to Hill's algorithm. I append a list of old
sources. I don't know which of them are still valid contact points.
If the data lend themselves to simple a priori hypotheses about what
factors control the patterns of variation, I'd recommend*:
CANOCO (Vegetatio 75:159-160.):
Cajo J.F. Ter Braak
Agricultural Mathematics Group
Box 100, 6700 AC Wageningen
The North American distributer:
111 Clover Lane Dept. 16
Ithaca, NY 14850 USA
Your friend might want to look at an article by Mike Palmer in the December
issue of _Ecology_:
Palmer, MW. 1993. Putting things in even better order: the advantages
of canonical correspondence analysis. Ecology 74(8): 221-2230.
According to Lee Belbin, Dan Faith, and Peter Minchin, we should all be
using modifications of global nonmetric multidimensional scaling (NMDS) for
these problems. The difficulty remains finding fast, robust, and cheap
software for doing NMDS in ways appropriate for vegetation data. Readily
available NMDS code (e.g., ALSCAL) uses a least squares algorithm that
negates most of its advantages in ecological situations where principal
components analysis and correspondence analysis produce highly curved or
Any bionet.plants readers have suggested sources for KYST-style NMDS code?
- Bob Knox
- Biospheric Sciences Branch, Code 923
- NASA/Goddard Space Flight Center, Greenbelt, MD 20771
- knox at spruce.gsfc.nasa.gov
Holcomb Research Institute
4600 Sunset Ave.
Indianapolis, Indiana 46208 USA
47 Waller Avenue
Toronto, Ontario M5S 1B8
PATN (large system of programs for numerical taxonomy and
CSIRO Division of Wildlife and Rangelands Research
P.O. Box 84, Lyneham, A.C.T.
DECORANA (public domain):
Forestry Sciences Laboratory
Oregon State University
* These recommendations and suggestions do not constitute an endorsement
of any product by the US Government or NASA or . . .