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The Method Tab

You can use the Method tab (Figure 19.5) to specify options for the thin-plate spline algorithm.

The following options are available:

Selection method

specifies how to choose the smoothing penalty parameter. This option corresponds to the SELECT= option in the MODEL statement.

GCV

selects the smoothing parameter that minimizes the generalized cross validation criterion.

Approx. model DF

selects the smoothing parameter for which the trace of the prediction matrix is closest to the Target model DF. This corresponds to SELECT=DF option.

Manual

enables you to specify the value in the log(n*lambda) field. This corresponds to the LOGNLAMBDA= option.

Maximum number of unique design points

specifies a limit on the number of unique design points, , in the model. This option corresponds to the DISTANCE= option in the MODEL statement in the following way: the value in this field is used to compute a value for the DISTANCE= option so that there are at most design points. This option is useful for large data sets, since the TPSPLINE procedure is computationally expensive.

Figure 19.5: The Method Tab