Can we say that clustering is a function?
Of course, the term "clustering" is broad and can mean different things in different contexts: clustering as an area in machine learning, clustering algorithm, clustering mathematical method, etc.
But, can we talk about a clustering function? Like we can talk about classification function and regression function ...
I think we can, in the following sense. Clustering is a function with input: set of objects, and output: set of clusters, memberships in clusters for each object, and also relations between clusters (in case of hierarchical clustering).
Let me know what you think.