Building Machine Learning Systems with Python - Third Edition

Obtaining useful predictions

It is not just customers who bought X also bought Y, even though that is how many online retailers phrase their recommendations (see the Amazon.com screenshot given earlier); a real system cannot work like this. Why not? Because such a system would get fooled by very frequently bought items and would simply recommend that which is popular without any personalization.

For example, at a supermarket, many customers buy bread every time they shop, or almost every time (for the sake of argument, let us say that 50 percent of visits end with the purchase of bread). So, if you focus on any particular item, say, dishwasher soap, and look at what is frequently bought with dishwasher soap, you might find that bread is frequently ...