@rawify/vector3/_/_vector.js

The RAW JavaScript 3D Vector library

var u = require("utils");

// Define Current Field to operate in: Z_7
var P = {
    add: function(x, y) {
        return u.math.mod(x + y, 7);
    },
    mul: function(x, y) {
        return u.math.mod(x * y, 7);
    },
    sub: function(x, y) {
        return u.math.mod(x - y, 7);
    }
};

// Simple Laplace determinant calculation
function determinant(A) {

    if (A.length < 2)
        return null;

    // Recursion end at 2x2 Matrix with ad-bc determinant
    if (A.length === 2) {
        return u.math.polysub(
                u.math.polymul(A[0][0], A[1][1], P),
                u.math.polymul(A[0][1], A[1][0], P), P);
    }

    // Little Helper, calculates the "Streichungsmatrix" - Matrix A without row R and column C
    function S(A, R, C) {

        var r = new Array(A.length - 1);
        for (var i = 0; i < A.length; i++) {

            if (i === R)
                continue;

            var m = i > R ? i - 1 : i;

            r[m] = new Array(A.length - 1);
            for (var j = 0; j < A.length; j++) {

                if (j === C)
                    continue;

                var n = j > C ? j - 1 : j;

                r[m][n] = A[i][j];
            }
        }
        return r;
    }
    // S([[1,2,3],[4,5,6],[7,8,9]], 0,0);

    var k = 0; // k's row
    var sum = [0, 0, 0]; // Result polynomial
    for (var i = 0; i < A.length; i++) { // Loop over the array
        sum = u.math.polyadd(sum,
                u.math.polymul(A[k][i],
                        u.math.polymul([Math.pow(-1, i + k)], determinant(S(A, k, i)), P), P), P);
    }
    return sum;
}

var A = [
    [[0], [1], [2], [3], [4]],
    [[6], [0], [2], [3], [4]],
    [[5], [5], [0], [1], [0, 1]],
    [[4], [4], [6], [0], [0, 3]],
    [[3], [3], [0, 6], [0, 4], [0]]
];

console.log(determinant(A));




/*
 determinant([
 [[4], [5]],
 [[3], [-2]]
 ]);*/