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306 Formula Editor Chapter 9
Using Functions
Generating Random Numbers
You can create formulas that generate real numbers by effectively “rolling the dice” within the
constraints of a specified distribution. Each time you click Apply in the formula editor window, these
functions produce a new set of random numbers.
Note: Random numbers are generated using the Mersenne-Twister technique. This technique has a
period length of 2 19937 -1. For details about the generators, see Matsumoto and Nishimura (1998). The
new generators are verified to pass all the DIEHARD tests as documented in Marshalled (1996).
To create a formula containing a random number
1 Open the formula editor by right-clicking a column name in the data grid and selecting Formula.
2 Select an expression in the formula editing area by clicking it. (It is selected when there is a red
outline around it.)
3 Click the menu on the function browser and select Random, as shown in Figure 9.18. The random
functions now appear in the list below the menu.
Figure 9.18 Select Random from the Function Browser List
4 Select which function to insert in the formula. For descriptions of each function, see “Random
Functions,” p. 485.
Using Dates and Times
JMP stores dates and times in numeric columns using the Macintosh standard of the number of seconds
since January 1, 1904. When a column has date values, you can assign a date format to that column by
double-clicking a column name and selecting Date or Time from the Format menu. See “Numeric
Format Options,” p. 63, for details.
To use dates and times in a formula:
1 Open the formula editor by right-clicking a column name in the data grid and selecting Formula.
2 Select an expression in the formula editing area by clicking it. (It is selected when there is a red