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pythonstatisticsprobability

Return the index corresponding to the median value from a list

I want to write a function median_index(A) that returns the index of the median given a distribution A ( A is a list with values associated with each index).

I have sorted out the way to get the median value but now I want to have the position (index) where that median is when the list A is sorted.

def median_index(P):
    l = sorted(P)
    l_len = len(P)
    if l_len < 1:
        return None
    if l_len % 2 == 0 :
        return ( l[(l_len-1)/2] + l[(l_len+1)/2] ) / 2.0
    else:
        return l[(l_len-1)/2]

median_index([0.12,0.04,0.12,0.12,0.2,0.16,0.16,0.08])

That produces 5 as the result. 5 is the last position where 0.12. This is the index of the median 0.12 when I sort the list and calculate the median which is 0.12.

Solution

  • You can use list.index(element)