mulColumn(index, value) {
                util.checkColumnIndex(this, index);
                for (var i = 0; i < this.rows; i++) {
                    this.set(i, index, this.get(i, index) * value);
                }
                return this;
            }
Multiplies the values of a column with a scalar
@param {number} index - Column index
@param {number} value
@return {Matrix} this