Modeling and Multivariate Methods - SAS

Chapter 24 Visualizing, Optimizing, and Simulating Response Surfaces 575
Special Profiler Topics
Expanding Intermediate Formulas
The Profiler launch dialog has an Expand Intermediate Formulas checkbox. When this is checked, then
when the formula is examined for profiling, if it references another column that has a formula containing
references to other columns, then it substitutes that formula and profiles with respect to the end
references—not the intermediate column references.
For example, when Fit Model fits a logistic regression for two levels (say A and B), the end formulas
(Prob[A] and Prob[B]) are functions of the Lin[x] column, which itself is a function of another column x. If
Expand Intermediate Formulas is selected, then when Prob[A] is profiled, it is with reference to x, not
Lin[x].
In addition, using the Expand Intermediate Formulas checkbox enables the Save Expanded Formulas
command in the platform red triangle menu. This creates a new column with a formula, which is the
formula being profiled as a function of the end columns, not the intermediate columns.
Linear Constraints
The Prediction Profiler, Custom Profiler and Mixture Profiler can incorporate linear constraints into their
operations. Linear constraints can be entered in two ways, described in the following sections.
Pop-up Menu Item
To enter linear constraints via the pop-up menu, select Alter Linear Constraints from either the Prediction
Profiler or Custom Profiler pop-up menu.
Choose Add Constraint from the resulting dialog, and enter the coefficients into the appropriate boxes. For
example, to enter the constraint p1 + 2*p2 ≤ 0.9, enter the coefficients as shown in Figure 24.23. As shown,
if you are profiling factors from a mixture design, the mixture constraint is present by default and cannot be
modified.
Figure 24.23 Enter Coefficients
Enter coefficients
After you click OK, the Profiler updates the profile traces, and the constraint is incorporated into
subsequent analyses and optimizations.
If you attempt to add a constraint for which there is no feasible solution, a message is written to the log and
the constraint is not added. To delete a constraint, enter zeros for all the coefficients.
Constraints added in one profiler are not accessible by other profilers until saved. For example, if constraints
are added under the Prediction Profiler, they are not accessible to the Custom Profiler. To use the
constraint, you can either add it under the Custom Profiler pop-up menu, or use the Save Linear
Constraints command described in the next section.