Renormalizes the array so that its L2 norm is 1 (up to computational errors). - Java Collection Framework

Java examples for Collection Framework:Array Element

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Description

Renormalizes the array so that its L2 norm is 1 (up to computational errors).

Demo Code


//package com.java2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        double[] v = new double[] { 34.45, 35.45, 36.67, 37.78, 37.0000,
                37.1234, 67.2344, 68.34534, 69.87700 };
        System.out.println(java.util.Arrays.toString(normalize(v)));
    }//from   ww w. j  ava 2 s.co  m

    /**
     * Renormalizes the array so that its L2 norm is 1
     * (up to computational errors).
     */
    public static double[] normalize(double[] v) {
        return (scalarMultiply(1.0 / norm(v), v));
    }

    /**
     * Returns a comma delimited string representing the value of the array.
     */
    public static String toString(double[] array) {

        StringBuffer buf = new StringBuffer(array.length);
        int i;
        for (i = 0; i < array.length - 1; i++) {
            buf.append(array[i]);
            buf.append(',');
        }
        buf.append(array[i]);
        return buf.toString();
    }

    /**
     * Returns a comma delimited string representing the value of the array.
     */
    public static String toString(double[][] array) {
        StringBuffer buf = new StringBuffer();
        for (int k = 0; k < array.length; k++) {
            buf.append(toString(array[k]));
            buf.append(System.getProperty("line.separator"));
        }
        return buf.toString();
    }

    /**
     * Returns a comma delimited string representing the value of the array.
     */
    public static String toString(int[] array) {
        StringBuffer buf = new StringBuffer(array.length);
        int i;
        for (i = 0; i < array.length - 1; i++) {
            buf.append(array[i]);
            buf.append(',');
        }
        buf.append(array[i]);
        return buf.toString();
    }

    /**
     * Returns a comma delimited string representing the value of the array.
     */
    public static String toString(int[][] array) {
        StringBuffer buf = new StringBuffer();
        for (int k = 0; k < array.length; k++) {
            buf.append(toString(array[k]));
            buf.append(System.getProperty("line.separator"));
        }
        return buf.toString();
    }

    /**
     * Multiplies every component of an array by a scalar.
     */
    public static double[] scalarMultiply(double a, double[] v) {
        double[] ans = new double[v.length];
        for (int k = 0; k < v.length; k++) {
            ans[k] = a * v[k];
        }
        return (ans);
    }

    /**
     * Multiplies every component of an array by a scalar.
     */
    public static double[] scalarMultiply(double a, int[] v) {
        double[] ans = new double[v.length];
        for (int k = 0; k < v.length; k++) {
            ans[k] = v[k] * a;
        }
        return (ans);
    }

    /**
     * Computes the L2 norm of an array (Euclidean norm or "length").
     */
    public static double norm(double[] data) {
        return (Math.sqrt(sumSquares(data)));
    }

    /**
     * Computes the L2 norm of an array (Euclidean norm or "length").
     */
    public static double norm(int[] data) {
        return (Math.sqrt(sumSquares(data)));
    }

    /**
     * Sums the squares of all components;
     * also called the energy of the array.
     */
    public static double sumSquares(double[] data) {
        double ans = 0.0;
        for (int k = 0; k < data.length; k++) {
            ans += data[k] * data[k];
        }
        return (ans);
    }

    /**
     * Sums the squares of all components;
     * also called the energy of the array.
     */
    public static double sumSquares(double[][] data) {
        double ans = 0.0;
        for (int k = 0; k < data.length; k++) {
            for (int l = 0; l < data[k].length; l++) {
                ans += data[k][l] * data[k][l];
            }
        }
        return (ans);
    }

    /**
     * Sums the squares of all components;
     * also called the energy of the array.
     */
    public static int sumSquares(int[] data) {
        int ans = 0;
        for (int k = 0; k < data.length; k++) {
            ans += data[k] * data[k];
        }
        return (ans);
    }

    /**
     * Sums the squares of all components;
     * also called the energy of the array.
     */
    public static int sumSquares(int[][] data) {
        int ans = 0;
        for (int k = 0; k < data.length; k++) {
            for (int l = 0; l < data[k].length; l++) {
                ans += data[k][l] * data[k][l];
            }
        }
        return (ans);
    }
}

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