Piecewise Polynomials and Splines

Fitted Natural Spline Model

• Each term 4 df (except famhist)

• Pointwise standard error curves

• Rugplot shows location of x values

Tensor Product Basis

DF = 1 +(4-1) + (4-1) = 7

DF = 4 x 4 = 16

Thin-Plate Spline

DF = 15

Red points are knots