Work with the Formula Editor

Formulas are used throughout Fathom for a variety of purposes. Any time you create or edit a formula, you use the same formula editor interface. You can use formulas to do the following:

Use a formula to …	Example
Determine the values of a new attribute.	Define an attribute, PopulationDensity, and give it the formula Population/Area or one of the Random Functions.
Define a filter.	Enter the formula sex = "M" to look at only the males in a collection of people. (see Write a Filter.)
Summarize data.	To summarize student heights, enter the formulas mean(height), median(height), and (max(height)+min(height))/2. See Add or Remove a Summary Table’s Formulas or Define a Measure.
Define a statistic.	To compare tomato plants grown in sunny locations with those grown in shady locations, enter this formula: (mean(height, loc = "sunny")–mean(height, loc = "shady").
Control a simulation.	Suppose you wanted to throw dice until there were 2 sixes. You would use an “until” command in the Collect Measures panel of a measures collection inspector with the formula count(face=6)=2.
Compute a slider value.	To make a slider that will choose a random integer between 1 and 100 each time its animation button is pressed, give it the formula randomInteger(1, 100).

With formulas, you don’t simply choose from a list of statistics or filters or simple computations. You can compute practically anything you want, as long as you know how to express it.