Dear Dave,
This modified version of TWINSPAN may be interesting for you when you
compare methods:
Modified TWINSPAN classification in which the hierarchy respects cluster
heterogeneity
Jan Roleček, Lubomír Tichý, David Zelený, Milan Chytrý 2009 Modified
TWINSPAN classification in which the hierarchy respects cluster
heterogeneity Journal of Vegetation Science 20(4): 596–602
http://onlinelibrary.wiley.com/doi/10.1111/j.1654-1103.2009.01062.x/abstract
Zoltan
2011.04.26. 23:40 keltezéssel, Dave Roberts írta:
Dear List,
Earlier this year on an (undoubtedly ill-advised) lark I coded up an R
version of TWINSPAN. It's far from a polished package at this point,
but the code does run. One of the interesting features is that you can
partition a PCO or NMDS in addition to the traditional CA. To be
clear, I am not a TWINSPAN fan either, but I wanted it for a methods
paper I was working on.
The problem is that I based the code on Hill, Bunch & Shaw (1975,
J of Ecol 63:597-613) which is what I had available. Apparently the
algorithm in the commercial TWINSPAN is significantly modified from
the original, but I couldn't find a description of the actual
algorithm anywhere in the literature. It is probably described in the
User Manual of the software, but I was not sufficiently motivated to
chase down a copy. I do have a copy of the FORTRAN code, but it was
apparently written in FORTRAN II, and is basically inscrutable, even
to an old FORTRAN dog like me.
So, if somebody has a clear description of the actual algorithm (and I
think it is disturbing that I could not find one), it would be
possible to code it up in native R. The alternative, to write a
wrapper for the original FORTRAN code is not a trivial task. I gave it
a couple of days and gave up.
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