[R] Extracting means for given strata from dissimilarity object

[Grum, Mikkel [IPGRI-SSA-Nairobi]]

Is there a way of extracting mean distance or dissimilarity for a given
strata from a 'dist' or 'dissimilarity' object, e.g. extract mean distances
for each species in Anderson's iris data? 

data(iris)
iris.dist<-dist(iris[,1:4])

then what?




Mikkel Grum, PhD
Genetic Diversity Scientist
International Plant Genetic Resources Institute (IPGRI)
Sub-Saharan Africa Group
***
PO Box 30677
Nairobi, Kenya
Tel: +254 2 524505(direct)/524500(IPGRI)
Fax: +254 2 524501(IPGRI)/524001(ICRAF)
m.grum at cgiar.org
www.ipgri.org