The operation spreads the core groups over the rest of the SOM. New neurons are bound to existing groups from their neighborhood based on the U-matrix distances. The closest neurons is enclosed to an group.
Example: As an example, four neurons have been selected for the cores of the groups. Then, the operation is used to collect the rest of the neurons to these groups.
... NDA> somsprd -s som -w som_W -c coreGroups -cout resGroups ...
Original Smoothed