Cubic Spline Smoother

The cubic spline scatterplot smoother is a special smoothing technique for 2D scatterplots, which generally produces a smooth generalization of the relationship between the two variables in the scatterplot. The cubic spline smoother is often used in generalized additive models, to estimate the unspecific (non-parametric) function of the predictor variables that best predicts the (transformed) dependent variable values.  Computational details regarding the cubic spline smoother, and comparisons to other smoothing algorithms, can be found in Hastie and Tibshirani, 1990, and Schimek, 2000.