Touché, but I still think they are not "so" different, as an ANOVA and...a SHEEP could be...;-) have to take care of my trees,
cheers, Andrés Gavin Simpson <gavin.simp...@ucl.ac.uk> escribió: > On Wed, 2011-04-13 at 15:01 +0200, Andres Mellado Diaz wrote: >> Hi, >> >> I think that TWINSPAN and IndVal are not so different (well, it's true >> that you can use your own a-priori clustering method in IndVal, >> because its use is independent of the classification method), in fact, >> TWINSPAN is cited 38 times in Dufrene & Legendre 1997 IndVal paper. >> They largely discuss differences and limitations between both methods >> throughout their article, > > ??? > > TWINSPAN /provides/ indicator values, but it is not its raison d'etre. > It *was* designed to *cluster* vegetation data in the two-way manner > Jari mentions and provides the indicator values as one of extra outputs. > In the past, one would have to use TWINSPAN to get indicator values > because there weren't many (any?) other options for computing them, but > if you wanted indicator values then you had to accept the TWINSPAN > clustering too - there was no either/or. > > IndVal changed that so you *could* compute good indicator values along > the same lines as TWINSPAN but without having to use it esoteric > clustering algorithm. Of course Dufrene and Pierre cite the TWINSPAN > paper a lot; they were producing a new tool that at the grossest level > did something (one part) that TWINSPAN did and therefore could be > compared against. > > Your entire email is focussed on one aspect of TWINSPAN and the > similarities between it and IndVal - you aren't seeing the woods for the > trees. TWINSPAN and IndVal are different beasts. > > To your argument I might offer the repost: "post hoc ergo propter > hoc" (in a bastardised way: TWINSPAN and IndVal give me indicator > values, therefore TWINSPAN and IndVal are the same. ;-) > > G > >> cheers >> >> Andrs >> >> Jari Oksanen <jari.oksa...@oulu.fi> escribi: >> >> > On 13/04/11 15:34 PM, "Gavin Simpson" <gavin.simp...@ucl.ac.uk> wrote: >> > >> >> On Wed, 2011-04-13 at 09:25 -0300, Diogo B. Provete wrote: >> >>> Dear Zang, >> >>> this procedure is not currently used, since Pierre Legendre and >> coleagues >> >>> developed a new metric called IndVal, which is available in the labdsv >> >>> package in R. >> >> >> >> I'm sorry, (I don't like TWINSPAN...) but to claim TWINSPAN is not used >> >> because it has been superseded by the IndVal approach is totally >> >> incorrect. >> >> >> >> TWINSPAN and IndVal do **very** different things; the former produces a >> >> cluster analysis that happens to churn out [a form of] indicator species >> >> values, whilst the latter **only** computes [a form of] indicator values >> >> - you have to supply the clustering. >> >> >> > Howdy all, >> > >> > Gavin is absolutely correct here (and I am not a TWINSPAN fan either). >> > >> > Various clustering methods are the closest thing to Twinspan in base R. >> > However, they don't provide you species clustering which makes Twinspan >> > unique. Twinspan works on the original community matrix and produces a >> > simultaneous classification for plots and species. I don't use >> > classification but casually, and I don't know if there are such >> simultaneous >> > two-way classification problems in R. Indval and friends for quite a >> > different problem, like Gavin wrote (twice). >> > >> > As far as I know, Twinspan is not available in R. Two persons have >> contacted >> > me and proposed to port Twinspan to R, and I have provided them the basic >> > files and promised to help them in the work, but I haven't heard >> anything of >> > the project after the initial contact. >> > >> > I do think that Twinspan is a suboptimal choice for classification >> problems, >> > but I won't go into details. I urge you to study its behaviour yourself if >> > get your hands on Twinspan. >> > >> > Cheers, Jari Oksanen >> > >> > _______________________________________________ >> > R-sig-ecology mailing list >> > R-sig-ecology@r-project.org >> > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology >> > >> >> _______________________________________________ >> R-sig-ecology mailing list >> R-sig-ecology@r-project.org >> https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > > -- > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% > Dr. Gavin Simpson [t] +44 (0)20 7679 0522 > ECRC, UCL Geography, [f] +44 (0)20 7679 0565 > Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk > Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ > UK. WC1E 6BT. [w] http://www.freshwaters.org.uk > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% > > -- Andrés Mellado DÃaz Centre for Hydrological Studies CEH-CEDEX Water Quality Department Pº bajo de la Virgen del Puerto, 3 28005, Madrid SPAIN [[alternative HTML version deleted]]
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