Model Browser User's Guide

Global Model Class: Free Knot Spline

This option is only available for global models with only one input factor. See also Hybrid Splines for a description of splines. The major difference is that you choose the position of the knots for hybrid splines; here the optimal knot positions are calculated as part of the fitting routine.

You can set the number of knots and the spline order can be between one and three.

There are three different algorithms under Optimization settings: Penalized least squares, Genetic algorithm, and Constrained least squares.

For all three methods, you can set the Initial population. This is the number of initial guesses at the knot positions. The other settings put limits on how long the optimization takes.

The example following shows a free knot spline model with three knots. The position of the knots is marked on the N axis.

See also the local models involving splines:

• Polynomial Spline
• Local Model Class: Truncated Power Series
• Local Model Class: Free Knot Spline

Global Model Class: Multiple Linear Models

Local Model Setup