I ran a cluster analysis on a population of customers. I used variables like:
- Spent amount
Now I'd like to use these clusters ('Little buyer', 'Regular fan of the brand A', ...) for segmentation purposes.
Problem: Future customers will appear, but I can't rerun a cluster analysis each day, so I need to assign the new customers to the current clusters.
Proposal: I can assign the future customers to the nearest centroid of the current clusters.
The new customers are assigned to clusters which have not been built for them, if the distribution of the new customers is not the same than the distribution of the current ones. Thus, the clustering is going to deteriorate.
Question: How can I monitor the evolution of the quality of the clustering / segmentation?
I was thinking about monitoring the evolution of the R-Squared (Coefficient of determination), because it's the metric I used to choose the actual clustering, but I'm not sure it's a best practice.