getColumn(index) {
                util.checkColumnIndex(this, index);
                var column = new Array(this.rows);
                for (var i = 0; i < this.rows; i++) {
                    column[i] = this.get(i, index);
                }
                return column;
            }
Returns a new array from the given column index
@param {number} index - Column index
@return {Array}