On Tue, Jul 30, 2013 at 11:11 AM, Pat Ferrel <p...@occamsmachete.com> wrote:
> [B'A] = > iphone ipad nexus galaxy surface > iphone 2 2 2 1 0 > ipad 2 2 2 1 0 > nexus 1 1 1 1 0 > galaxy 1 1 1 1 0 > surface 0 0 0 0 1 > > The rows are what we want from [B'A] since the row items are from B, right? > Yes. It is easier to understand if you have different kinds of items as well as different actions. For instance, suppose that you have user x query terms (A) and user x device (B). B'A is then device x term so that there is a row per device and the row contains terms. This is good when searching for devices using terms.
