Returns the computed median value of an array.
All of the values in the input array are used. The input array is first histogrammed using numbins bins. The bin containing the median is selected by searching for the halfway point in the cumulative histogram. The median value is then computed by linearly interpolating across that bin.
a : array
numbins : int
A floating point value approximating the median. :
[CRCProbStat2000] Section 2.2.6