Because it is based on nearest neighbors rather than a defined radius, compounds which are in relatively sparse UMAP areas may have neighbors from a chemically distant cluster. In this case, if all kNNs come from the same cluster, and this cluster exhibits similar properties, this can skew the measure to some extent. This artifact can be avoided by instead using a defined radius and a variable number of kNNs while ignoring compounds which have no kNNs within the specified radius.