Hi!

According to Clarke and Warwick (Clarke, K. R. and Warwick, R. M. 2001. 
Change in marine communities: an approach to statistical analysis and 
interpretation. PRIMER-E, Plymouth) you could consider the following 
rough rule-of-thumb:
stress< 0.05: excellent representation; stress < 0.1: good 
representation, although the fine structure of any compact groups may 
deserve closer examination; stress < 0.2: acceptable representation, 
though for values at the upper end of this range conclusions should be 
compared with those from an alternative mehtod (e.g. cluster analysis); 
stress > 0.3: unsatisfactory representation, indicating that the points 
are close to being placed in random positions.
Nevertheless you should take into account that the stress usually 
increases with increasing quantity of data.

HTH

Cheers,

Maria Dulce Subida

 

 



Gian Maria Niccolò Benucci escribió:
> Okey, really many thanks... So having low Stress value is foundamental, as
> it is as lower as higher the model fit the data, is that right? How can I
> know if my Stress is correct? I mean, if it is enough low to asses that the
> model fit good the samples data shifts into the graph...
> Is there a treshold or something?
> I would appreciate any pdf or kind of reviews on ordination models for
> community ecology data... :)
> Thank you really much!
> Cheers,
>
> Gian
>
>
> 2009/12/1 Gian Maria Niccolò Benucci <gian.benucci@gmail.com>
>
>   
>> Hi Hi there,
>>
>> I am trying to use funcion metaMDS (vegan pakage) for Community Ecology
>> data, but I find no way to calculate the "expressed variance" of the first 2
>> axis? is there a way to do that?
>> Thanks a lot in advance,
>>
>> Gian
>>
>>
>>
>>     
>
>
>   
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