Modeling and Multivariate Methods - SAS

Chapter 9 Performing Nonlinear Regression 267
Fit a Custom Model
Clicking Make Formula at this point (after using Show Points) creates a new column in the data table.
This column has the formula as a function of the latest parameter starting values.
Note: If you click Make Formula before using the Show Graph or Show Points buttons, you are asked to
provide the X and Y roles, and an optional Group role. See Figure 9.16. After that, you are brought back to
the plot so you have the opportunity to adjust the parameters starting values if desired. At that point click
Make Formula again to create the new column.
Once the formula is created in the data table, continue the analysis by assigning the new column as the
X, Predictor Formula in the Nonlinear launch dialog.
Customize the Nonlinear Model Library
The Model Library is created by a built-in script named NonlinLib.jsl, located in the Resources/Builtins
folder in the folder that contains JMP (Windows) or in the Application Package (Macintosh). You can
customize the nonlinear library script by modifying this script.
To add a model, you must add three lines to the list named Listofmodellist#. These three lines are
actually a list themselves, which consists of the following three parts.
• Model name, a quoted string
• Model formula, an expression
• Model scale
For example, suppose you want to add a model called “Simple Exponential Growth” that has the form
y = b 1
e kx
Add the following lines to the NonlinLib.jsl script
{//Simple Exponential Growth
"Simple Exponential Growth",
Expr(Parameter({b1=2, k=0.5}, b1*exp(k * :X))),
lowx = -1; highx = 2; lowy = 0; highy = 2},
Some things to note:
• The first line is simply an open bracket (starting the list) and an optional comment. The second line is
the string that is displayed in the model library window.
• The values of lowx, highx, lowy, and highy specify the initial window for the theoretical graph.
• There is a comma as the last character in the example above. If this is the final entry in the
Listofmodellist# list, the comma can be omitted.
• If the model uses more than two parameters, replace the last line (containing the graph limits) with the
quoted string “String Not Available”.
To delete a model, delete the corresponding three-lined list from the Listofmodellist# list.