	This is part of the clusters module
	It is only available if you configure PLUMED with ./configure –enable-modules=clusters . Furthermore, this feature is still being developed so take care when using it and report any problems on the mailing list.

Setup a vector that has one for all the atoms that form part of the cluster of interest and that has zero for all other atoms.

CLUSTERS	the label of the action that does the clustering
CLUSTER	( default=1 ) which cluster would you like to look at 1 is the largest cluster, 2 is the second largest, 3 is the the third largest and so on.

LOWMEM

( default=off ) this flag does nothing and is present only to ensure back-compatibility