Example 2: Determination of an optimum \text{ARIMA} model via Grid search

This is the same as Example 1, except now class autoARIMA uses Method 2 with a possible seasonal adjustment. As a result, the unadjusted model with p = 3, q = 2, s = 1, d = 0 is chosen as optimum.

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

public class AutoARIMAEx2 {
	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;
		int[] arOrders = {0, 1, 2, 3};
        int[] maOrders = {0, 1, 2, 3};
		int[] periods = {1, 2};
        int[] orders = {0, 1, 2};

		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.setMaximumARLag(5);
		autoArima.setPeriods(periods);
		autoArima.setDifferenceOrders(orders);
		autoArima.compute(arOrders, maOrders);
	    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 2: Grid search with "+
			              "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("%5sParameters%n", " ");
		System.out.printf(Locale.ENGLISH, " constant:%10.6f%n", constant);
        for (int i=0; i<ar.length; i++)
          System.out.printf(" ar[%d]:%13.6f%n", i, ar[i]);
        for (int i=0; i<ma.length; i++)
          System.out.printf(" ma[%d]:%13.6f%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 2: Grid search with differencing

Optimum Model: p=3, q=2, s=1, d=0

Number of outliers:  1

Outlier statistics:
 Time    Type
  109       0

AIC:  408.108176
RSE:    0.412456

     Parameters
 constant:  0.554459
 ar[0]:     1.940615
 ar[1]:    -1.898025
 ar[2]:     0.897791
 ma[0]:     1.115803
 ma[1]:    -0.911902


      * * * Forecast Table * * *
  Exact   forecast     limits        psi
 8.7000     9.1085     0.8084     0.8248
 8.6000     9.1715     1.0479     0.6145
 9.3000     9.5039     1.1597     0.5248
 9.1000     9.7677     1.2349     0.5926
 8.8000     9.7051     1.3245     0.7056
 8.5000     9.3817     1.4421     0.7157
Link to Java source.