# Nonlinear Regression Parameters

Parameters are the parts of your model that the Nonlinear Regression procedure estimates. Parameters can be additive constants, multiplicative coefficients, exponents, or values used in evaluating functions. All parameters that you have defined will appear (with their initial values) on the Parameters list in the main dialog box.

**Name.** You must specify a name for each parameter. This name must be a
valid variable name and must be the name used in the model expression
in the main dialog box.

**Starting Value.** Allows you to specify a starting value for the parameter, preferably
as close as possible to the expected final solution. Poor starting
values can result in failure to converge or in convergence on a solution
that is local (rather than global) or is physically impossible.

**Use starting values
from previous analysis.** If you have already run a nonlinear
regression from this dialog box, you can select this option to obtain
the initial values of parameters from their values in the previous
run. This permits you to continue searching when the algorithm is
converging slowly. (The initial starting values will still appear
on the Parameters list in the main dialog box.)

*Note*:
This selection persists in this dialog box for the rest of your session.
If you change the model, be sure to deselect it.

Specifying Nonlinear Regression Parameters

This feature requires Custom Tables and Advanced Statistics.

- From the menus choose:
- In the Nonlinear Regression dialog box, click Parameters.
- Enter a name for the parameter. This name must be a valid variable name and must be the name used in the model expression in the main dialog box.
- Enter a starting value for the parameter, preferably as close as possible to the expected final solution. Poor initial values can result in failure to converge or in convergence on a solution that is local (rather than global) or is physically impossible.
- After specifying a name and starting value, click Add to add the parameter to the Parameters list.