SampleCheck.java

package jaea.optimization.sampling;

import jaea.optimization.tools.Utils;

/**
 * Function to check if the sampled data is well-sampled
 * 
 * @author Le Minh Nghia, NTU-Singapore
 * 
 */
public class SampleCheck {
	/**
	 * Check if the data is from stratified sampling
	 * 
	 * @param samplePoints
	 *            Matrix of sample points: row = number of samples, col =
	 *            dimensions
	 * @param lowerBound
	 *            Lower bounds on each dimension
	 * @param upperBound
	 *            Upper bounds on each dimension
	 * @param nBin
	 *            Bins for discretization
	 * @return TRUE if Stratified Samples, FALSE if otherwise
	 */
	static public boolean isStratifiedSample(double[][] samplePoints,
			double[] lowerBound, double[] upperBound, int nBin) {
		boolean res = true;
		int nSample = samplePoints.length;
		int nDim = samplePoints[0].length;
		double[] binWidth = new double[nDim];
		for (int i = 0; i < nDim; i++) {
			if (Utils.eq(upperBound[i], lowerBound[i]))
				return false;
			binWidth[i] = (upperBound[i] - lowerBound[i]) / nBin;
		}
		int indexDim;

		double[][] SampleIndexes = new double[nBin][nDim];
		for (int i = 0; i < nBin; i++)
			for (int j = 0; j < nDim; j++)
				SampleIndexes[i][j] = 0;
		try {
			for (int i = 0; i < nSample; i++) {
				double[] chrom = samplePoints[i];
				for (int j = 0; j < nDim; j++) {
					indexDim = (int) Math.floor((chrom[j] - lowerBound[j])
							/ binWidth[j]);
					if (indexDim == nBin)
						indexDim = nBin - 1;

					SampleIndexes[indexDim][j] += 1;
				}
			}
		} catch (Exception e) {
			System.err.println("Error at Stratified Sample checking... "
					+ e.getMessage());
			System.exit(0);
		}
		// Utils.DMat2File("test.csv", SampleIndexes);
		/* Checking if all 'hypersquares' are filled */
		for (int i = 0; i < nBin; i++)
			for (int j = 0; j < nDim; j++)
				if (SampleIndexes[i][j] == 0)
					return false;
		return res;
	}

	/**
	 * Check if the data is from Latin hyper-cube sampling
	 * 
	 * @param samplePoints
	 *            Matrix of sample points: row = number of samples, col =
	 *            dimensions
	 * @param lowerBound
	 *            Lower bounds on each dimension
	 * @param upperBound
	 *            Upper bounds on each dimension
	 * @return TRUE if Stratified Samples, FALSE if otherwise
	 */
	static public boolean isLHSample(double[][] samplePoints,
			double[] lowerBound, double[] upperBound) {
		boolean res = true;
		int nSample = samplePoints.length;
		int nDim = samplePoints[0].length;
		double[] binWidth = new double[nDim];
		for (int i = 0; i < nDim; i++) {
			if (Utils.eq(upperBound[i], lowerBound[i]))
				return false;
			binWidth[i] = (upperBound[i] - lowerBound[i]) / nSample;
		}
		int indexDim;
		double[][] SampleIndexes = new double[nSample][nDim];
		for (int i = 0; i < nSample; i++)
			for (int j = 0; j < nDim; j++)
				SampleIndexes[i][j] = 0;
		for (int i = 0; i < nSample; i++) {
			double[] chrom = samplePoints[i];
			for (int j = 0; j < nDim; j++) {
				indexDim = (int) Math.floor((chrom[j] - lowerBound[j])
						/ binWidth[j]);
				if (indexDim == nSample)
					indexDim = nSample - 1;
				SampleIndexes[indexDim][j] = i + 1;
			}
		}
		// Utils.DMat2File("test.csv", SampleIndexes);
		/* Checking */
		for (int i = 0; i < nSample; i++)
			for (int j = 0; j < nDim; j++)
				if (SampleIndexes[i][j] == 0)
					return false;
		return res;
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		double[][] samples = Utils.File2DoubleMat("p112.csv");
		int nSample = samples.length;
		int nDim = samples[0].length;
		double[] lowB = new double[nDim];
		double[] highB = new double[nDim];
		for (int i = 0; i < nDim; i++) {
			lowB[i] = Double.MAX_VALUE;
			highB[i] = -Double.MAX_VALUE;
		}
		for (int i = 0; i < nSample; i++)
			for (int j = 0; j < nDim; j++) {
				if (samples[i][j] < lowB[j])
					lowB[j] = samples[i][j];
				if (samples[i][j] > highB[j])
					highB[j] = samples[i][j];
			}
		/*
		 * for (int j = 0; j < nDim; j++) { highB[j] += 0.01*Math.abs(highB[j]);
		 * }
		 */

		boolean res = SampleCheck.isLHSample(samples, lowB, highB);
		if (res == true)
			System.out.println("IS LH Sampling");
		else
			System.out.println("IS NOT LH Sampling");
		res = SampleCheck.isStratifiedSample(samples, lowB, highB, nDim);
		if (res == true)
			System.out.println("IS Stratified Sampling");
		else
			System.out.println("IS NOT Stratified Sampling");
	}

}