iWork® '09 For Dummies®

Chapter 14. Using Formulas and Functions

In This Chapter

• Creating formulas

• Using summary formulas

• Working with functions

• Using a lookup function

One of the most important features of any spreadsheet is the ability to place formulas into cells. Other spreadsheets, such as Microsoft Excel, offer functions and formulas — often the same ones you find in Numbers. Spreadsheet users expect to find a SUM function along with a TODAY function and all the other functions that they're accustomed to, particularly if they switch back and forth between spreadsheet applications or if they're sharing their documents. What sets Numbers apart is the ease with which you can create and manage formulas along with the large number of templates that implement sophisticated uses of formulas and functions.

Starting to Use Formulas

Formulas can contain specific values (called constants and sometimes literals); they also can contain references to cells in the spreadsheet. If a formula contains a reference to a cell, every time that cell's value is updated, the formula is reevaluated. A formula can contain a reference to a cell that itself contains a formula. There is no limit to the number of formulas in the chain of formulas for a given cell. Whenever the first value in the chain is changed, every formula is reevaluated. The only limitation to this chain of formulas is that it has to be a single path. You can't create what is called a circular reference, a formula that relies on evaluating a previous cell that contains ...