Basic Analysis and Graphing - SAS

Chapter 4 Performing Bivariate Analysis 109
Fit Each Value
Local Smoother Report
The Local Smoother report contains the R-Square for the kernel smoother fit and the Sum of Squares
Error. You can use these values to compare the kernel smoother fit to other fits, or to compare different
kernel smoother fits to each other.
Table 4.10 Description of the Local Smoother Report
R-Square
Sum of Squares Error
Local Fit (lambda)
Weight Function
Smoothness (alpha)
Robustness
Measures the proportion of variation accounted for by the kernel smoother
model. For more information, see “Statistical Details for the Smoothing Fit
Reports” on page 126.
Sum of squared distances from each point to the fitted kernel smoother. It is
the unexplained error (residual) after fitting the kernel smoother model.
Select the polynomial degree for each local fit. Quadratic polynomials can
track local bumpiness more smoothly. Lambda is the degree of certain
polynomials that are fitted by the method. Lambda can be 1 or 2.
Specify how to weight the data in the neighborhood of each local fit. Loess
uses tri-cube. The weight function determines the influence that each xi and yi
has on the fitting of the line. The influence decreases as xi increases in
distance from x and finally becomes zero.
Controls how many points are part of each local fit. Use the slider or type in a
value directly. Alpha is a smoothing parameter. It can be any positive number,
but typical values are 1/4 to 1. As alpha increases, the curve becomes
smoother.
Reweights the points to deemphasize points that are farther from the fitted
curve. Specify the number of times to repeat the process (number of passes).
The goal is to converge the curve and automatically filter out outliers by
giving them small weights.
Related Information
• “Fitting Menus” on page 115
Fit Each Value
The Fit Each Value command fits a value to each unique X value. The fitted values are the means of the
response for each unique X value.
Fit Each Value Report
The Fit Each Value report shows summary statistics about the model fit.