How to Use the Formula Editor

Briefly

Enter attribute names or functions by typing or double-clicking in the list. Numbers and operators are in the keypad. Click OK to close the box and apply the formula. Never enter the left-hand side of a formula.

What To Enter

A formula in Fathom is just the right-hand side of your equation or function. Do not enter the left-hand side or the equals sign. So if you want "speed = distance / time," just open the formula for speed and enter distance / time, as shown.

The Computer Keyboard

You can enter your formula on the keyboard if you wish - it goes right into the formula pane.

Here is some information on Keyboard Shortcuts.

The Formula Pane

Here is where you enter your formula. You can enter it by typing or by using the function list.

The Function List

This pane lists the attributes you have to work with as well as the many functions Fathom recognizes. Press the headings (boxes with plusses in them) to open up a list. To enter a function or attribute, double-click it. In the picture, we've just double-clicked time. To learn what a function does, select it (single click) and look in the help pane.

Here you can get access to global values, that is, the values of sliders.

Here is information on Fathom's Built-In Functions.

Here is information on Fathom's Special Values.

The Keypad

Enter numbers and many operators on this keypad. Hold down (Windows) or (Mac) to cause some keys to become alternates (e.g. the period key becomes a comma key).

The Help Pane

This pane shows information about whatever is selected in the function list.

Operators

Fathom supports comparison operators such as =, >, and <. For some expressions, you may want to use Boolean (and, or, not) operators or conditional (if) functions.

If the expression you write is either true or false (such as x > y, 3 = 4, Sex = "F") you can use it in a filter or a conditional expression. If the result is a number (such as x * y, 3 - 4) it's an appropriate attribute value.

Use Parentheses!

Most mistakes you can make are because things aren't grouped properly. Use parentheses liberally. Typing ( creates a pair of parentheses. And if something is selected when you press (, the selection gets parenthesized.

The Selection Principle

If you select an expression, the next thing you type either replaces it or modifies the whole expression. For example, if you have x + 3 selected, and you type a parenthesis, you get (x + 3). If you type /2, you get (x + 3)/2. But if you type a, you get a.