On 7/22/2010 2:21 PM, Graves, Gregory wrote:
Among those users of Primer, stress values greater than 0.3 are interpreted as "questionable". Using both isoMDS and metaMDS (vegan package), the stress values returned are much higher using my own data and using examples provided in R Help. For example Rstress = 8.3, and the stressplot r2 = 0.99 indicating (to me) that the ordination is OK. I am guessing that the "stress" values across packages are not the same, and googling about has not returned a satisfactory answer ... thus this posting. My concern being that reporting a stress value of 8 for what I consider a satisfactory result may raise a few Primer-user's eyebrows.
Dear Gregory, as the help file of ?isoMDS tells us: "stress The final stress achieved (in percent)" So 8.3 is in reality 0.083. Thomas Petzoldt ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
