So someone unearthed a scratchpaper grid Joanne Rowling used to plot the “J. K. Rowling” Harry Potter books. The columns of intersecting characters and themes remind us that all advertising components are interrelated. One fallacy direct-response marketers may fall into is to think they can isolate all communication elements — search, print, radio, TV, online display, mobile, social media, PR — from each other to track individual channel response. It’s a nice theory, but all ripples on the lake of consumer interest send waves elsewhere. Each media character has unique measurable value, but is also influenced by others. Just ask Harry.