### 7.1.4 The median: median

Although the average of a list of numbers typically means the mean,
there are other notions of “average”. Another one is the median;
the median of a list of numbers is the middle number when they are
listed in numeric order. For example, the median of the list
[1,2,5,7,20] is simply 5. If the length of a list of numbers is
even, so there isn’t a middle number, the median is then the mean of
the two middle numbers; for example, the median of [1,2,5,7,20,21] is
(5+7)/2 = 6.

The median function finds the median of a list. The command

median([1,2,5,7,20])

will return

5

The median function can take weights with a second argument,
where the weight of number represents how many times it is counted in
a list. For example,

median([1,2,5,7,20],[5,3,2,1,2])

will return

2

since the median of 1,1,1,1,1,2,2,2,5,5,7,20,20 is 2.