source: src/main/java/agents/uk/ac/soton/ecs/gp4j/util/ArrayUtils.java

package agents.uk.ac.soton.ecs.gp4j.util;

import agents.org.apache.commons.math.stat.StatUtils;

public class ArrayUtils extends agents.org.apache.commons.lang.ArrayUtils {
        public static double[][] combine(double[][] combinations, double[] addition) {
                double[][] result;

                if (combinations == null || combinations.length == 0) {
                        result = new double[addition.length][1];

                        for (int i = 0; i < addition.length; i++)
                                result[i][0] = addition[i];
                } else {
                        result = new double[combinations.length * addition.length][combinations[0].length + 1];

                        for (int i = 0; i < combinations.length; i++) {
                                for (int j = 0; j < addition.length; j++) {
                                        System.arraycopy(combinations[i], 0, result[i
                                                        * addition.length + j], 0, combinations[0].length);
                                        result[i * addition.length + j][result[0].length - 1] = addition[j];
                                }
                        }

                }
                return result;
        }

        public static int[][] combine(int[][] combinations, int[] addition) {
                int[][] result;

                if (combinations == null || combinations.length == 0) {
                        result = new int[addition.length][1];

                        for (int i = 0; i < addition.length; i++)
                                result[i][0] = addition[i];
                } else {
                        result = new int[combinations.length * addition.length][combinations[0].length + 1];

                        for (int i = 0; i < combinations.length; i++) {
                                for (int j = 0; j < addition.length; j++) {
                                        System.arraycopy(combinations[i], 0, result[i
                                                        * addition.length + j], 0, combinations[0].length);
                                        result[i * addition.length + j][result[0].length - 1] = addition[j];
                                }
                        }

                }
                return result;
        }

        public static int[][] allCombinations(int[][] values) {
                int result[][] = combine(null, values[0]);

                for (int i = 1; i < values.length; i++)
                        result = combine(result, values[i]);

                return result;
        }

        public static int[][] allCombinations(int[] values, int repetitions) {
                int[][] input = new int[repetitions][values.length];

                for (int i = 0; i < input.length; i++) {
                        input[i] = values;
                }

                return allCombinations(input);
        }

        public static double[][] allCombinations(double[][] values) {
                double result[][] = combine(null, values[0]);

                for (int i = 1; i < values.length; i++)
                        result = combine(result, values[i]);

                return result;
        }

        public static double[] linspace(double min, double max, int sampleCount) {
                if (sampleCount == 1)
                        return new double[] { (max - min) / 2 };

                double[] samples = new double[sampleCount];
                double increment = (max - min) / (sampleCount - 1);
                samples[0] = min;
                samples[samples.length - 1] = max;

                for (int i = 1; i < sampleCount - 1; i++)
                        samples[i] = samples[i - 1] + increment;

                return samples;
        }

        public static double[] log(double[] array) {
                double[] result = new double[array.length];

                for (int i = 0; i < array.length; i++)
                        result[i] = Math.log(array[i]);

                return result;
        }

        public static double[] exp(double[] array) {
                double[] result = new double[array.length];

                for (int i = 0; i < array.length; i++)
                        result[i] = Math.exp(array[i]);

                return result;
        }

        public static double[] normalize(double[] array) {
                double sum = StatUtils.sum(array);
                return divide(array, sum);
        }

        public static double[] divide(double[] array, double scalar) {
                double[] result = new double[array.length];

                for (int i = 0; i < array.length; i++) {
                        result[i] = array[i] / scalar;
                }

                return result;
        }
}