Java Array Normalize normalize(double[] v)

Description

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

License

Open Source License

Declaration

public static double[] normalize(double[] v) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    /**/*from ww w.  j  a v a2s.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));
    }

    /**
     * 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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