ml-matrix/src/dc/util.js

Matrix manipulation and computation library

'use strict';

exports.hypotenuse = function hypotenuse(a, b) {
    if (Math.abs(a) > Math.abs(b)) {
        var r = b / a;
        return Math.abs(a) * Math.sqrt(1 + r * r);
    }
    if (b !== 0) {
        var r = a / b;
        return Math.abs(b) * Math.sqrt(1 + r * r);
    }
    return 0;
};

// For use in the decomposition algorithms. With big matrices, access time is
// too long on elements from array subclass
// todo check when it is fixed in v8
// http://jsperf.com/access-and-write-array-subclass
exports.getEmpty2DArray = function (rows, columns) {
    var array = new Array(rows);
    for (var i = 0; i < rows; i++) {
        array[i] = new Array(columns);
    }
    return array;
};

exports.getFilled2DArray = function (rows, columns, value) {
    var array = new Array(rows);
    for (var i = 0; i < rows; i++) {
        array[i] = new Array(columns);
        for (var j = 0; j < columns; j++) {
            array[i][j] = value;
        }
    }
    return array;
};