Example 48.2: Wampler Data

The ORTHOREG Procedure

Example 48.2: Wampler Data

This example applies the ORTHOREG procedure to a collection of data sets noted for being ill conditioned. The OUTEST= data set is used to collect the results for comparison with values certified to be correct by the National Institute of Standards and Technology (1997).

Note: The results from this example vary from machine to machine depending on floating-point configuration.

The data are from Wampler (1970). The independent variates for all five data sets are xⁱ, i = 1, ... 5, for x = 0,1, ... , 20. Two of the five dependent variables are exact linear functions of the independent terms:

$y_1 & = & 1 + x + x^2 + x^3 + x^4 + x^5 \ y_2 & = & 1 + 0.1x + 0.01x^2 + 0.001x^3 + 0.0001x^4 + 0.00001x^5 \$

The other three dependent variables have the same mean value as y₁, but with nonzero errors.

$y_3 & = & y_1 + e\ y_4 & = & y_1 + 100{e}\ y_5 & = & y_1 + 10000{e}\$

where e is a vector of values with standard deviation 2044, chosen to be orthogonal to the mean model for y₁.

The following statements create a SAS data set Wampler containing the Wampler data, run a SAS macro program using PROC ORTHOREG to fit a fifth-order polynomial in x to each of the Wampler dependent variables, and collect the results in a data set named ParmEst.

   data Wampler;
      do x=0 to 20;
         input e @@;
         y1 = 1 +       x    +        x**2 +      x**3
                +       x**4 +        x**5;
         y2 = 1 + .1   *x    + .01   *x**2 + .001*x**3
                + .0001*x**4 + .00001*x**5;
         y3 = y1 +       e;
         y4 = y1 +   100*e;
         y5 = y1 + 10000*e;
         output;
      end;
      datalines;
   759 -2048 2048 -2048 2523 -2048 2048 -2048 1838 -2048 2048
   -2048 1838 -2048 2048 -2048 2523 -2048 2048 -2048 759
   ;

   %macro WTest;
      data ParmEst; if (0); run;
      %do i = 1 %to 5;
         proc orthoreg data=Wampler outest=ParmEst&i noprint;
            model y&i = x x*x x*x*x x*x*x*x x*x*x*x*x;
         data ParmEst&i; set ParmEst&i; Dep = "y&i";
         data ParmEst; set ParmEst ParmEst&i;
            label Col1='x'     Col2='x**2'  Col3='x**3'
                  Col4='x**4'  Col5='x**5';
         run;
      %end;
   %mend;
   %WTest;

Instead of displaying the raw values of the RMSE and parameter estimates, use a further DATA step to compute the deviations from the values certified to be correct by the National Institute of Standards and Technology (1997).

   data ParmEst; set ParmEst;
      if      (Dep = 'y1') then
         _RMSE_ = _RMSE_ - 0.00000000000000;
      else if (Dep = 'y2') then
         _RMSE_ = _RMSE_ - 0.00000000000000;
      else if (Dep = 'y3') then
         _RMSE_ = _RMSE_ - 2360.14502379268;
      else if (Dep = 'y4') then
         _RMSE_ = _RMSE_ - 236014.502379268;
      else if (Dep = 'y5') then
         _RMSE_ = _RMSE_ - 23601450.2379268;
      if (Dep ^= 'y2') then do;
         Intercept = Intercept - 1.00000000000000;
         Col1      = Col1      - 1.00000000000000;
         Col2      = Col2      - 1.00000000000000;
         Col3      = Col3      - 1.00000000000000;
         Col4      = Col4      - 1.00000000000000;
         Col5      = Col5      - 1.00000000000000;
      end;
      else do;
         Intercept = Intercept - 1.00000000000000;
         Col1      = Col1      - 0.100000000000000;
         Col2      = Col2      - 0.100000000000000e-1;
         Col3      = Col3      - 0.100000000000000e-2;
         Col4      = Col4      - 0.100000000000000e-3;
         Col5      = Col5      - 0.100000000000000e-4;
      end;
   proc print data=ParmEst label noobs;
      title 'Wampler data: Deviations from Certified Values';
      format _RMSE_ Intercept Col1-Col5 e9.;
      var Dep _RMSE_ Intercept Col1-Col5;
   run;

The results, shown in Output 48.2.1, indicate that the values computed by PROC ORTHOREG are quite close to the NIST-certified values.

Output 48.2.1: Wampler data: Deviations from Certified Values

Wampler data: Deviations from Certified Values

Dep	_RMSE_	Intercept	x	x2**	x3**	x4**	x5**
y1	0.00E+00	5.46E-12	-9.82E-11	1.55E-11	-5.68E-13	3.55E-14	-6.66E-16
y2	0.00E+00	8.88E-16	-3.19E-15	1.24E-15	-1.88E-16	1.20E-17	-2.57E-19
y3	-2.09E-11	-7.73E-11	1.46E-11	-2.09E-11	2.50E-12	-1.28E-13	2.66E-15
y4	-4.07E-10	-5.38E-10	8.99E-10	-3.29E-10	4.23E-11	-2.27E-12	4.35E-14
y5	-3.35E-08	-4.10E-08	8.07E-08	-2.77E-08	3.54E-09	-1.90E-10	3.64E-12

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