The third data set, partly shown in Table 3.3, contains data about 240 orders in a café. Each row corresponds to one customer order. The columns refer to products. For instance, the first customer ordered a cappuccino and a muffin. This example is quite generic and analyzing such a data set is generally referred to as market basket analysis. For example, one can think of analyzing the product combinations pur- chased in a supermarket or in an electronic bookstore. Cafés, supermarkets, book- stores, etc. may be interested in the following questions:
• Which products are frequently purchased together?
• When do people buy a particular product?
• Is it possible to characterize typical customer groups?
• How to promote the sales of products with a higher margin?