Data Smoothing: Loess

Plots Tab

You can use the Plots tab to create plots that graphically display results of the Loess analysis. (See Figure 18.4.) The raw residuals are computed as $Y - \hat{Y}$, where $\hat{Y}$ indicates the variable that contains the predicted values of the response.

Creating a plot often adds one or more variables to the data table. The following plots are available:

Observed vs. Explanatory with smoother


creates a scatter plot of the X and Y variables, overlaid with a smoother.

Confidence limits for means


specifies whether to add 95% upper and lower confidence limits to the Observed vs. Explanatory plot.

Observed vs. Predicted


creates a scatter plot of the Y variable versus the predicted values.

Raw residuals vs. Predicted


creates a scatter plot of the residuals versus the predicted values.

Raw residuals vs. Explanatory


creates a scatter plot of the residuals versus the X variable.

Residual normal QQ


creates a normal Q-Q plot of the residuals.

Smoothing criterion vs. Smoothing parameter


creates a scatter plot of the smoothing criterion (for example, AICC) versus the smoothing parameter value for all smoothing parameter values examined in the selection process. The value that minimizes the criterion is indicated by a star-shaped marker.

Note: SAS/IML Studio adds a smoother to an existing scatter plot when both of the following conditions are satisfied:

  • The scatter plot is the active window when you select the analysis.

  • The scatter plot variables match the analysis variables.