R help - Jan 2006 - R function for Gap statistic

Dear All,

I need to calculate the optimal number of clusters for a classification 
based on a large number of observations (tens of thousands). Thibshirani et 
al. proposed the gap statistic for this purpose. Is any R code or fucntion 
available for this? Any help would be appreciated, including suggestions 
about other alternatives for the selection of an optimal number of cluster 
from large datasets.

Thanks, 

 Norman Goodacre