Model Browser User's Guide

Local Model Class: Truncated Power Series

This is only available for a single input factor.

You can choose the order of the polynomial basis function and the number of knots for Truncated Power Series Basis Splines. A spline is a piecewise polynomial, where different sections of polynomial are fitted smoothly together. The point of each break is called a knot. The truncated power series changes the coefficient for the highest power when the input passes above the knot value.

It is truncated because the power series is an approximation to an infinite sum of polynomial terms. You can use infinite sums to approximate arbitrary functions, but clearly it is not feasible to fit all the coefficients.

Click Polynomial to see (and remove, if you want) the polynomial terms. One use of the remove polynomial term function is to make the function linear until the knot, and then quadratic above the knot. In this case we remove the quadratic coefficient.

See also

• Polynomial Spline, where you can choose different order basis functions either side of the knot
• Hybrid Splines, a global model where you can choose a spline order for one of the factors (the rest have polynomials fitted)
• Local Model Class: Free Knot Spline, free knot splines with cubic basis functions, where you can choose the number of knots

Local Model Class: Polynomials and Polynomial Splines

Local Model Class: Free Knot Spline