Table 2. Detailed comparison between automatic and expert classifications.

Reference classification	Num. clust.	Homogeneity	Joining probability
SCOP SF	779	85.2	68.0
CATH SF	885	81.1	66.4
SCOP or CATH SF	-	86.3	69.1
SCOP folds	466	92.0	44.5
CATH folds	473	91.4	10.7
SCOP or CATH folds	-	95.4	45.0

First column: reference classification. Second column: Number of clusters in the reference classification. Third column: Percentage of the 779 clusters in the automatic classification that are pure with respect to the reference classification (in case of CATH or SCOP, it is the fraction of clusters that are pure with respect to either CATH or SCOP). Fourth column: Percentage of the pairs joined in the reference classification that are joined in the automatic classification. In the case of folds, only pairs in different superfamilies are counted.