package de.lmu.ifi.dbs.elki.math.statistics.dependence;

/*
 This file is part of ELKI:
 Environment for Developing KDD-Applications Supported by Index-Structures

 Copyright (C) 2015
 Ludwig-Maximilians-Universität München
 Lehr- und Forschungseinheit für Datenbanksysteme
 ELKI Development Team

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import static org.junit.Assert.assertEquals;

import java.util.Arrays;

import org.junit.Test;

import de.lmu.ifi.dbs.elki.JUnit4Test;
import de.lmu.ifi.dbs.elki.utilities.datastructures.arraylike.ArrayLikeUtil;

/**
 * Validate correlation by comparing to the results of R.
 * 
 * @author Erich Schubert
 * @since 0.4.0
 */
public class SpearmanCorrelationDependenceMeasureTest implements JUnit4Test {
  double[][] data = { //
  { 1, 2, 3, 4 }, //
  { 1, 3, 5, 700 }, //
  { 400, 3, 2, 1 }, //
  { 1, 400, 2, 3 }, //
  { 100, 0, 0, 100 }, //
  };

  double[][] R = { //
  { 1. }, //
  { 1., 1. }, //
  { -1., -1., 1. }, //
  { 0.4, 0.4, -0.4, 1. }, //
  { 0., 0., 0., -0.4472136, 1 }, //
  };

  @Test
  public void testSpearmanCorrelation() {
    DependenceMeasure cor = SpearmanCorrelationDependenceMeasure.STATIC;
    // Single computations
    for(int i = 0; i < data.length; i++) {
      for(int j = 0; j <= i; j++) {
        double co = cor.dependence(data[i], data[j]);
        assertEquals("Cor does not match for " + i + "," + j, R[i][j], co, 1e-7);
      }
    }
    // Bulk computation
    double[] mat = cor.dependence(ArrayLikeUtil.DOUBLEARRAYADAPTER, Arrays.asList(data));
    for(int i = 0, c = 0; i < data.length; i++) {
      for(int j = 0; j < i; j++) {
        double co = mat[c++];
        assertEquals("Cor does not match for " + i + "," + j, R[i][j], co, 1e-7);
      }
    }
  }
}
