User`s guide

Refining Linear Parametric Models
Refining Linear Parametric Models
In this section...
“When to Refine Models” on page 3-103
“What You Specify to Refine a Model” on page 3-103
“How to Refine Linear Parametric Models in the GUI” on page 3-104
“How to Re fi ne Linear Parametric Models at the Command Line” on page
3-105
When to Refine Models
There are two situations where you can refine estimates of linear parametric
models.
In the first situation, you have already estimated a parametric model and
wish to refine the model. However, if your model captures the essential
dynamics, it is usually not necessary to continue improving the fit—especially
when the improvement is a fraction of a percent.
In the second situation, you might have con structe d a model using one of
the m odel constructors described in “Commands for Constructing Model
Structures” on page 2-13. In this case, you built initial parameter guesses into
the m odel structure and wish to refine these parameter values.
Note Because it is difficult to specify nonlinear model parameters in
advance, you typically only estimate nonlinear models.
What You Specify to Refine a Model
When you refine a model, you must provide two inputs:
• Parametric model
• Data — You can either use the same data set for refining the model as the
one you originally used to estimate the model, or you can use a different
data set.
3-103