The GAM Procedure

PROC GAM Statement

Subsections:

Global Plot Options
Specific Plot Options

PROC GAM <options>;

The PROC GAM statement invokes the procedure. Table 41.1 summarizes the options available in the PROC GAM statement.

Table 41.1: PROC GAM Statement Options

Option	Description
DATA=	Specifies the input SAS data set
DESCENDING	Reverses the sort order of all CLASS variables
ORDER=	Specifies the sort order for CLASS variables
PLOTS	Controls plots produced through ODS Graphics

You can specify the following options.

DATA=SAS-data-set

specifies the SAS data set to be read by PROC GAM. The default value is the most recently created data set.

DESCENDING DESC

reverses the sort order of all classification variables (specified in the CLASS statement). If both the DESCENDING and ORDER= options are specified, PROC GAM orders the categories according to the ORDER= option and then reverses that order. This option has the same effect as the classification variable option DESCENDING in the CLASS statement and the response variable option DESCENDING in the MODEL statement.

ORDER=DATA | FORMATTED | FREQ | INTERNAL

specifies the sort order for the levels of all classification variables (specified in the CLASS statement). This ordering determines which parameters in the model correspond to each level in the data. Note that the ORDER= option in the CLASS statement and the ORDER= response variable option in the MODEL statement override the ORDER= option in the PROC GAM statement.

PLOTS <(global-plot-options)> <= plot-request <(options)>> PLOTS <(global-plot-options)> <=(plot-request <(options)> <…plot-request <(options)>>)>

controls the plots produced through ODS Graphics. When you specify only one plot-request, you can omit the parentheses around the plot-request. Here are some examples:

plots=all

plots=components(commonaxes)

plots(unpack)=components(commonaxes clm)

ODS Graphics must be enabled before plots can be requested. For example:

ods graphics on;

proc gam data=test plots(unpack)=components(commonaxes clm);
   model z=spline(x) spline(y);
run;

ods graphics off;

For more information about enabling and disabling ODS Graphics, see the section Enabling and Disabling ODS Graphics in Chapter 21: Statistical Graphics Using ODS.

With ODS Graphics enabled, PROC GAM produces by default a panel of plots of partial prediction curves of smoothing components.

Global Plot Options

The global-plot-options apply to all plots generated by the GAM procedure, unless altered by a specific-plot-option.

UNPACK: separately displays the smoothing component plots that are by default presented in panels. Use this option if you want to access individual smoothing component plots within the panel.

Specific Plot Options

The following listing describes the specific plots and their options.

ALL

requests that all plots be produced.

NONE

suppresses all plots.

COMPONENTS | COMPONENT <(components-options)>

displays a panel of smoothing component plots. The following components-options are available:

ADDITIVE: produces the additive component plots for spline and loess effects. The additive component plots combine the linear trend and the nonparametric prediction for each spline or loess effect.
CLM: includes confidence limits in the smoothing component plots. By default, 95% confidence limits are produced, but you can change the significance level by specifying the ALPHA= option in the MODEL statement. Note that producing these limits can be computationally intensive for large data sets.
COMMONAXES: specifies that smoothing component plots use a common vertical axis. This enables you to visually judge relative effect size.
UNPACK: displays the smoothing components individually.