MODEL PROGRAM Command (NLR command)

The MODEL PROGRAM command assigns initial values to the parameters and signifies the beginning of the model program. The model program specifies the nonlinear equation that is chosen to model the data. There is no default model.

  • The model program is required and must precede the [C]NLR command.
  • The MODEL PROGRAM command must specify all parameters in the model program. Each parameter must be individually named. Keyword TO is not allowed.
  • Parameters can be assigned any acceptable variable name. However, if you intend to write the final parameter estimates to a file with the OUTFILE subcommand, do not use the name SSE or NCASES (see OUTFILE Subcommand (NLR command)).
  • Each parameter in the model program must have an assigned value. The value can be specified on MODEL PROGRAM or read from an existing parameter data file named on the FILE subcommand.
  • Zero should be avoided as an initial value because it provides no information about the scale of the parameters. This situation is especially true for CNLR.
  • The model program must include at least one command that uses the parameters and the independent variables (or preceding transformations of these) to calculate the predicted value of the dependent variable. This predicted value defines the nonlinear model. There is no default model.
  • By default, the program assumes that PRED is the name assigned to the variable for the predicted values. If you use a different variable name in the model program, you must supply the name on the PRED subcommand (see PRED Subcommand (NLR command)).
  • In the model program, you can assign a label to the variable holding predicted values and also change its print and write formats, but you should not specify missing values for this variable.
  • You can use any computational commands (such as COMPUTE, IF, DO IF, LOOP, END LOOP, END IF, RECODE, or COUNT) or output commands (WRITE, PRINT, or XSAVE) in the model program, but you cannot use input commands (such as DATA LIST, GET, MATCH FILES, or ADD FILES).
  • Transformations in the model program are used only by [C]NLR, and they do not affect the active dataset. The parameters that are created by the model program do not become a part of the active dataset. Permanent transformations should be specified before the model program.