/**
* Determines whether a Matrix is diagonal or not.<br><br>
*
* Diagonal Matrix is a Matrix in which the entries outside the main diagonal
* are all zero. Note that the term diagonal refers to rectangular diagonal.<br><br>
*
* The result is cached.
* @memberof Matrix
* @instance
* @param {number} [digit=8] - Number of significant digits
* @returns {boolean} Returns rue if the Matrix is diagonal Matrix
*/
function isDiagonal(digit = this._digit) {
if (this._isDiagonal !== undefined) {
return this._isDiagonal;
}
const EPSILON = 1 / ((10 ** digit) * 2);
const A = this._matrix;
const [row, col] = this.size();
if (row === 0) {
this._isDiagonal = true;
return true;
}
for (let i = 0; i < row; i++) {
for (let j = 0; j < col; j++) {
if (i !== j && Math.abs(A[i][j]) >= EPSILON) {
this.isDiagonal = false;
return false;
}
}
}
this._isDiagonal = true;
return true;
};
module.exports = isDiagonal;