I hope someone here can help with the following:
I have a list of sale-like events. Each event is characterized by the customer-ID and the product they have purchased - out of a list of 100-odd different products. (As well as dates and such but those are irrelevant for this question).
What I would like to do is simply count how many clients have purchased both product A and product B in their lifetimes where A and B are any two combinations of products.
Thank you very much for any suggestions.