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Chapter 9 Formula Editor 289
Using Local Variables
Using Local Variables
You can create and use temporary numeric variables in expressions. You can use ordinary local variables
or you can use parameters, which are special types of local variables. Local variables exist only for the
evaluation of the formula in which they are defined. They appear in formulas as bold italic terms.
Local variables are most often used with Assignment functions, which can assign expressions to local
variables that are used in a complex equation. (See “Using Assignment Functions,” p. 309, for details.)
This technique can sometimes simplify building an equation and improve the efficiency of its
evaluation.
To build a formula that references values found in local variables
Step 1: Create the Local Variable
1 Open the formula editor by right-clicking a column name in the data grid and selecting Formula.
2 Select a box 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 formula element browser and select Local Variables from the formula
element browser menu.
4 Click New Local Variable.
5 Type a name for the local variable. By default, local variables have the names t0, t1, and so on, and
have missing values.
6 Assign a starting value, and click OK.
7 (Optional) To copy, edit, or delete a local variable, right-click (Ctrl-click on the Macintosh) its name
and select Copy, Edit, or Delete.
Step 2: Insert a Local Variable Into a Formula
1 Select a term in the formula editing area by clicking it. (It is selected when there is a red outline
around it.)
2 Click the local variable name in the Local Variables list. It appears in the formula as a bold italic
term.
9Formulas
Note: Another way to create local variables is to use the button on the formula editor keypad,
which automatically creates and displays local variables and places a semicolon after it. See “Adding
Operators,” p. 291, for details.
See “Using Local Variables in a Formula,” p. 323, for an example of referencing local variables in a
formula.
Incorporating Parameters
Parameters are special types of local variables that are recognized as model parameters in some
platforms, like Nonlinear fitting. They can be used in formulas just as ordinary local variables can.
To view examples of parameters
1 In the Sample Data folder that was installed when you installed JMP, open the Nonlinear Examples
folder and then US Population.jmp.