Abbott Ira Katz is a native New Yorker living in London, He has been teaching Excel for 25 years, exploring the application with learners on both sides of the Atlantic. He has authored two Apress books on Excel-Microsoft Excel 2010, and Excel 2010 Made Simple, he wrote the spreadsheetjournalism.com blog, and has contributed Excel-themed pieces to datajournalism.com, the Irish Tech News, datadrivenjournalism.net, and the baseball journal By the Numbers. His work with spreadsheets has been cited by the Guardian, the Wall Street Journal, the Freakonomic blog, and the Excel expert Chandoo, and he gave an Excel-driven, five-session workshop on Data Stories at Sciences Po University in Paris in 2018. Abbott has a doctorate in sociology from SUNY Stony Brook. The idea for a book on dynamic array functions springs from a sense that the take-up of these potent tools remains small, and that large numbers of spreadsheet users remain unaware of their capacity for facilitating a myriad of wide-ranging tasks.