**
LOWESS
**

This durable set of base routines, written in Fortran in the late 1970s, are widely used. They smooth just as a function of one predictor for data with normal errors or for data with long-tailed symmetric errors (robust fitting). Statistics for inference are not computed. S-Plus, R, Systat, XploRE, Gauss, and SAS have interfaces to LOWESS.

**
LOWESS base software
**
from netlib.

**
SAS macro
**
from Michael Friendly.

LOWESS was introduced in
** Visual and Computational Considerations in Smoothing
Scatterplots by Locally Weighted Fitting**.
W. S. Cleveland. In
* Computer Science and Statistics: Eleventh Annual
Symposium on the Interface*, pages 96-100.
Institute of Statistics, North Carolina State University,
Raleigh, North Carolina, 1978.
** Robust Locally Weighted Fitting and Smoothing Scatterplots**.
W. S. Cleveland.
* Journal of the American Statistical Association*,
74:829-836, 1979.

Computational methods were developed in
** LOWESS: A Program for Smoothing Scatterplots by Robust
Locally Weighted Fitting**.
W. S. Cleveland.
* The American Statistician*, 35:54, 1981.
and implemented in the above base software.

**
LOESS
**

The base software is a collection of C and Fortran subroutines that carry out local fitting for normal and long-tailed distributions and for one or more predictors. It also computes the statistics for inferences. S-PLUS has a complete implementation of LOESS as part of its modeling language.

**
LOESS base software
**
from netlib.

**
User's manual
**
in postscript from netlib.

LOESS was introduced in
** Locally-Weighted Fitting: An Approach to Fitting
Analysis by Local Fitting**.
W. S. Cleveland and S. J. Devlin.
* Journal of the American Statistical Association*,
83:596-610, 1988.

Computational methods were developed in
** Computational Methods for Local Fitting**.
W. S. Cleveland and E. Grosse.
* Statistics and Computing*, 1:47-62, 1991,
and implemented in the above base software.

The S-PLUS functions for LOESS are described in
** Statistical Models in S. **
W. S. Cleveland, E. Grosse, and M. Shyu,
edited by J. Chambers and T. Hastie, 309-376, Chapman and Hall, 1992.

**
LOCFIT
**

Clive Loader's marvelous base software, written in C, is by far the most ambitious. It computes fits and statistics for a wide range of distributions, including normal, long-tailed, binomial, exponential, and Poisson. It also computes density estimates. It can be used as stand-alone program with its own interface, or as a library in the S-PLUS or R systems. The code, documentation, and discussion are at

LOCFIT
(as well as the fundamentals, methods,
and theory of smoothing)
is described in
** Local Fitting and Likelihood**.
Clive R. Loader. Springer.

**
STL
**

STL is a procedure, based on loess, for decomposing a seasonal time series into a seasonal and other components specified by the user. The base software is written in Fortran. S-PLUS has an interface.

**
STL base software
**
from netlib.

STL was introduced in
**
STL: A Seasonal-Trend Decomposition Procedure Based on Loess (with Discussion)
**.
R. B. Cleveland, W. S. Cleveland, J. E. McRae, and I. Terpenning.
* Journal of Official Statistics*, 6:3-73, 1990.