Example 1: Determination of an optimum \text{AR}(p) model

This example uses time series LNU03327709 from the US Department of Labor, Bureau of Labor Statistics. It contains the unadjusted special unemployment rate, taken monthly from January 1994 through September 2005. The values 01/2004 - 03/2005 are used by class autoARIMA for outlier detection and parameter estimation. In this example, method 1, without seasonal adjustment, is chosen to find an appropriate AR(p) model. A forecast is done for the following six months and compared with the actual values 04/2005 - 09/2005.

import java.util.*;
import com.imsl.stat.*;

public class AutoARIMAEx1 {
  public static void main(String args[]) throws Exception {
	 int nOutliers;
	 double aic, RSE, constant;
	 int[] optimumModel;
	 int[][] outlierStatistics;
	 double[] outlierForecast, ar, ma;
     double[] psiWeights, probabilityLimits;

 
	 double[] x = {
         12.8, 12.2, 11.9, 10.9, 10.6, 11.3, 11.1, 10.4, 10.0, 9.7, 9.7, 9.7,
         11.1, 10.5, 10.3, 9.8, 9.8, 10.4, 10.4, 10.0, 9.7, 9.3, 9.6, 9.7,
         10.8, 10.7, 10.3, 9.7, 9.5, 10.0, 10.0, 9.3, 9.0, 8.8, 8.9, 9.2,
         10.4, 10.0, 9.6, 9.0, 8.5, 9.2, 9.0, 8.6, 8.3, 7.9, 8.0, 8.2,
         9.3, 8.9, 8.9, 7.7, 7.6, 8.4, 8.5, 7.8, 7.6, 7.3, 7.2, 7.3,
         8.5, 8.2, 7.9, 7.4, 7.1, 7.9, 7.7, 7.2, 7.0, 6.7, 6.8, 6.9,
         7.8, 7.6, 7.4, 6.6, 6.8, 7.2, 7.2, 7.0, 6.6, 6.3, 6.8, 6.7,
         8.1, 7.9, 7.6, 7.1, 7.2, 8.2, 8.1, 8.1, 8.2, 8.7, 9.0, 9.3,
         10.5, 10.1, 9.9, 9.4, 9.2, 9.8, 9.9, 9.5, 9.0, 9.0, 9.4, 9.6,
         11.0, 10.8, 10.4, 9.8, 9.7, 10.6, 10.5, 10.0, 9.8, 9.5, 9.7, 9.6,
         10.9, 10.3, 10.4, 9.3, 9.3, 9.8, 9.8, 9.3, 8.9, 9.1, 9.1, 9.1,
         10.2, 9.9, 9.4};
    
	 double[] exactForecast = {8.7, 8.6, 9.3, 9.1, 8.8, 8.5};

	 int[] times = {
         1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
         13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
         25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
         37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
         49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,
         61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72,
         73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84,
         85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96,
         97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108,
         109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120,
         121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132,
         133, 134, 135};
	  
	 AutoARIMA autoArima = new AutoARIMA(times, x);
	 autoArima.setCriticalValue(3.8);
	 autoArima.compute(5);
	 autoArima.forecast(6);

	 nOutliers = autoArima.getNumberOfOutliers();
	 aic = autoArima.getAIC();
	 optimumModel = autoArima.getOptimumModelOrder();
	 outlierStatistics = autoArima.getOutlierStatistics();
	 RSE = autoArima.getResidualStandardError();
	 outlierForecast = autoArima.getForecast();
     psiWeights = autoArima.getPsiWeights();
     probabilityLimits = autoArima.getDeviations();
     constant = autoArima.getConstant();
     ar = autoArima.getAR();
     ma = autoArima.getMA();

     System.out.printf("%nMethod 1: Automatic AR model selection"+
		               ", no differencing%n");
     System.out.printf("%nOptimum Model: p=%d, q=%d, s=%d, d=%d%n",
		                 optimumModel[0], optimumModel[1],
						 optimumModel[2], optimumModel[3]);
	 System.out.printf("%nNumber of outliers:%3d%n%n", nOutliers);
     System.out.printf("Outlier statistics:%n");
     System.out.printf(" Time%4sType%n", " ");
     for (int i=0; i<nOutliers; i++)
       System.out.printf("%5d%8d%n", outlierStatistics[i][0],
		                 outlierStatistics[i][1]);
     System.out.printf(Locale.ENGLISH, "%nAIC:%12.6f%n", aic);
     System.out.printf(Locale.ENGLISH, "RSE:%12.6f%n%n", RSE);
     System.out.printf("%6sParameters%n", " ");
     System.out.printf(Locale.ENGLISH, " constant:%12.6f%n", constant);
     for (int i=0; i<ar.length; i++)
		 System.out.printf(Locale.ENGLISH, " ar[%d]:%15.6f%n", i, ar[i]);
     for (int i=0; i<ma.length; i++)
		 System.out.printf(Locale.ENGLISH, " ma[%d]:%15.6f%n", i, ma[i]);

     System.out.printf("%n%n%6s* * * Forecast Table * * *%n", " ");
     System.out.printf("%2sExact%3sforecast%5slimits%8spsi%n",
		               " ", " ", " ", " ");
     for (int i=0; i<outlierForecast.length; i++)
		 System.out.printf(Locale.ENGLISH, "%7.4f%11.4f%11.4f%11.4f%n",
		         exactForecast[i], outlierForecast[i],
				 probabilityLimits[i], psiWeights[i]);
  }
}

Output


Method 1: Automatic AR model selection, no differencing

Optimum Model: p=5, q=0, s=1, d=0

Number of outliers:  7

Outlier statistics:
 Time    Type
    8       2
   13       0
   37       3
   85       0
   97       0
  109       0
  121       0

AIC:  371.104679
RSE:    0.359632

      Parameters
 constant:    0.097541
 ar[0]:       0.891872
 ar[1]:      -0.123830
 ar[2]:      -0.138262
 ar[3]:       0.135621
 ar[4]:       0.224111


      * * * Forecast Table * * *
  Exact   forecast     limits        psi
 8.7000     9.1076     0.7049     0.8919
 8.6000     9.0993     0.9445     0.6716
 9.3000     9.4032     1.0565     0.3503
 9.1000     9.5806     1.0849     0.2416
 8.8000     9.5506     1.0982     0.4243
 8.5000     9.3932     1.1382     0.5910
Link to Java source.