[R] Kruskal's MDS results

[Dieter Vanderelst]

Hi Michael,

Thanks for the reply.

I understand that the stress is a measure of how good the algorithm managed to represent the ordinal distances between items. And I also see why it's dependent on the number of dimensions. 

I was hoping someone could tell me exactly what the formula for the percentual stress is. To me it's not clear how this metric is calculated.

Regards,
Dieter


Michael Denslow wrote:
> Hi Dieter,
> 
> I'll take a shot at this. As I understand it, the stress is telling
> you how the ordination distances compare with original
> dissimilarities that you calculated.
> 
> It is a measure how well your ordination has done in representing the
> relationship of your sites. Note that the stress will differ
> depending on how many dimensions are used. I believe the default is k
> = 2 in isoMDS.
> 
> Hope this helps, Michael
> 
> 
>> Dear List,
>> 
>> I'm trying to interpret the results of the Kruskal's Non-metric
>> Multidimensional Scaling algorithm (isoMDS, MASS package).
>> 
>> The 'goodness of fit' is reported as "The final stress achieved (in
>> percent)".
>> 
>> What does this mean exactly? I've tried to google for an answer but
>> I've not come up with a definitive answer.
>> 
>> Regards, Dieter
>> 
>> 
>> -- Dieter Vanderelst PhD Student
>> 
>> Active Perception Lab University of Antwerp 
>> http://batbits.webnode.com/
>> 
>> Postal Address: Prinsstraat 13 B-2000 Antwerp Belgium
> 
> Michael Denslow
> 
> Graduate Student I.W. Carpenter Jr. Herbarium [BOON] Department of
> Biology Appalachian State University Boone, North Carolina U.S.A.
> 
> -- AND --
> 
> Communications Manager Southeast Regional Network of Expertise and
> Collections sernec.org
> 
> 
>