ziko/src/math/matrix/helpers/inverse.js

A versatile JavaScript library offering a rich set of Hyperscript Based UI components, advanced mathematical utilities, interactivity ,animations, client side routing and more ...

export function matrix_inverse(M) {
    if(M.row !== M.cols) throw Error('is not a square matrix"')
    if (M.det === 0) throw Error("determinant should not equal 0");
    const { arr } = M
    if (arr.length !== arr[0].length) return;
    var i = 0, ii = 0, j = 0, dim = arr.length, e = 0;
    var I = [], C = [];
    for (i = 0; i < dim; i += 1) {
        I[I.length] = [];
        C[C.length] = [];
        for (j = 0; j < dim; j += 1) {
            if (i == j) I[i][j] = 1;
            else I[i][j] = 0;
            C[i][j] = arr[i][j];
        }
    }
    for (i = 0; i < dim; i += 1) {
        e = C[i][i];
        if (e == 0) {
            for (ii = i + 1; ii < dim; ii += 1) {
                if (C[ii][i] != 0) {
                    for (j = 0; j < dim; j++) {
                        e = C[i][j];
                        C[i][j] = C[ii][j];
                        C[ii][j] = e;
                        e = I[i][j];
                        I[i][j] = I[ii][j];
                        I[ii][j] = e;
                    }
                    break;
                }
            }
            e = C[i][i];
            if (e == 0) return;
        }
        for (j = 0; j < dim; j++) {
            C[i][j] = C[i][j] / e;
            I[i][j] = I[i][j] / e;
        }
        for (ii = 0; ii < dim; ii++) {
            if (ii == i) {
                continue;
            }
            e = C[ii][i];
            for (j = 0; j < dim; j++) {
                C[ii][j] -= e * C[i][j];
                I[ii][j] -= e * I[i][j];
            }
        }
    }
    return new M.constructor(I);
}