When the direct option is not specified, a computationally faster method is used. This faster method performs local fitting at vertices of a kd tree decomposition of the predictor space followed by blending of the local polynomials to obtain a regression surface. Such iterations are appropriate when there are outliers in the data or when the error distribution is a symmetric long-tailed distribution. The default number of iterations is 1. The default is NONE, in which case no scaling is applied.
NONE is specified.
A separate fit is obtained for each smoothing value specified. All rights reserved.