Nonparametric Methods in Statistics with SAS Applications

LOESS REGRESSION 85

three-dimensional scatterplot is produced by these lines of code:

proc g3d data=plaza;

scatter income*grocery=entmt/ color="black";

run;

Here is the graph.

18

5.00

60

103

145

0.30

5.87

11.43

17.00

Entmt

11.67

18.33

25.00

Income

Grocery

To fit and plot the loess surface, they create a data set containing the grid points that

span the range of the data: 18 to 45 for income and 5 to 25 for grocery expenditure.

data grid points;

do income=18 to 145 by 1;

do grocery=5 to 25 by 1;

output;

end;

end;

run;

Next, the analysts run the loess procedure that creates a file named score results

containing predicted values for all the specified grid points.

proc loess data=plaza; ...