iWork '09: The Missing Manual

Editing Formulas

When you’re doing very simple math on neighboring cells—adding up a row or column, for example—quick formulas are all you need. However, as helpful as this automatic formula mixology might be, Numbers’ quick formulas and instant calculations can handle only very simple equations. When you require something even slightly more sophisticated—another type of calculation or working with nonadjacent cells—it’s time to build your own formula. This section introduces you to the basics of editing formulas, along with the tools that Numbers offers for making the job go easier.

Anatomy of a Formula

A formula is an equation, a statement that says, “this cell’s value is equal to this calculation.” To signal its status as an equation, every formula starts with the = sign. Numbers figures out the value of whatever follows that = sign and presents it to you in the cell containing the formula, the formula cell. The simplest possible formula is:

=1

Numbers strains its mighty math muscles to evaluate the right side of the = sign and arrives at the startling conclusion that the value is in fact one. The cell’s value is thus treated and displayed as one.

Note

Technically, the cell’s “real” value is the formula itself. But for display purposes and when the cell is used in other cell’s formulas, Numbers considers its value to be the calculated value.

Setting a cell’s value to a specific number by using a formula is not especially exciting or even terribly helpful (it’s of course easier to type ...