At a previous $dayjob at a very large financial institution, it's however many clusters are present in the strategy that was agreed to by the exec team and their highly paid consultants.
You find that many clusters and shoehorn the consultant provided categories on to the k clusters you obtain.
To be fair finding K is highly domain dependent and I would argue should not be for the analyst (solely) to decide, but with a feedback from domain experts.
You find that many clusters and shoehorn the consultant provided categories on to the k clusters you obtain.