Returns the median of a set of numbers. In a set containing an uneven number of values, the median will be the number in the middle of the set and in a set containing an even number of values, it will be the mean of the two values in the middle of the set.
返回给定的数值集合的中值。参数集合的数字个数为奇数时，中值为居于参数集合中间的数。当数字个数为偶数时，中值为居于中间的两个数的平均值。