Efficient method to calculate the rank vector of a list in Python

Question

I\'m looking for an efficient way to calculate the rank vector of a list in Python, similar to R\'s rank function. In a simple list with no ties between the ele

Answer 1

This doesn't give the exact result you specify, but perhaps it would be useful anyways. The following snippet gives the first index for each element, yielding a final rank vector of [0, 1, 2, 2, 2, 5, 6]

def rank_index(vector):
    return [vector.index(x) for x in sorted(range(n), key=vector.__getitem__)]

Your own testing would have to prove the efficiency of this.