A good deal of Excel's popularity is due to the collection of functions it provides. Functions are built-in, specialized algorithms that you can incorporate into your own formulas to perform powerful calculations. Functions work like miniature computer programs—you supply the data, and the function performs a calculation and gives you the result.
In some cases, functions just simplify calculations that you could probably perform on your own. For example, most people know how to calculate the average of several values, but when you're feeling a bit lazy, Excel's built-in AVERAGE() function automatically gives you the average of any cell range. Even more usefully, Excel functions perform feats that you probably wouldn't have a hope of coding on your own, including complex mathematical and statistical calculations that predict trends—hidden relationships in your data that you can use to make guesses or predict the future.
You can create your own Excel functions by writing a series of instructions using VBA (Visual Basic for Applications) code. Chapter 29 shows you how.
Every function provides a slightly different service. For example, one of Excel's statistical functions is named COMBIN(). It's a specialized tool used by probability mathematicians to calculate the number of ways a set of items can be combined. Although this sounds technical, even ordinary folks can use COMBIN() to get some interesting information. You can use the COMBIN() function, for example, to count the ...