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Fit Analyses |

For smoothing spline, kernel, and fixed bandwidth
local polynomial smoothers, SAS/INSIGHT software
derives the smoothing parameter from a
constant *c* that is independent of the units of **X**.
For a loess smoother, the smoothing parameter
is a positive constant .

With two explanatory variables in the model,
is called a *surface smoother*.
SAS/INSIGHT software provides nonparametric
surface estimates from thin-plate smoothing spline and kernel smoothers.
The explanatory variables are scaled by their corresponding
sample interquartile ranges. The smoothing parameter is derived from a constant *c* and both are independent
of the units of **X**.

Similar to parametric regression, the *R ^{2}*
value for an estimate is calculated as

You can use the following methods to choose the value:

**DF**- uses the value that makes the resulting smoothing
estimate have the specified degrees of freedom (
*df*).

**GCV**- uses the value that minimizes the generalized
cross validation (GCV) mean squared error.

**C Value**- uses the value derived from the
specified
*c*value for nonparametric smoothers other than the loess smoother.

**Alpha**- uses the specified value for the loess estimator.

If you specify a

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