Lance-Williams matrix-update formula

The various SAHN methods differ in the way in which the proximity between clusters is defined in step 1 and how the merged pair is represented as a single cluster in step 3. The proximity calculation in step 3 typically uses the Lance-Williams matrix-update formula ... 

Table 1 Parameter Values for Some Common SAHN Methods Defined by the Lance-Williams Matrix Update Formula"...

All of the SAHN methods can be implemented using a standard stored matrix approach, in which an initial intermolecule similarity matrix is progressively updated as new clusters are formed by the fusion of pairs of molecules and/or clusters molecules. The intercluster similarities are calculated using the Lance—Williams matrix-update formula ... 

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