Can numpy's argsort give equal element the same rank?

Question

I want to get the rank of each element, so I use argsort in numpy:

np.argsort(np.array((1,1,1,2,2,3,3,3,3)))
array([0, 1, 2, 3, 4, 5, 6         


        

Answer 1

I've written a function for the same purpose. It uses pure python and numpy only. Please have a look. I put comments as well.

def my_argsort(array):
    # this type conversion let us work with python lists and pandas series
    array = np.array(array)
    # create mapping for unique values
    # it's a dictionary where keys are values from the array and
    # values are desired indices 
    unique_values = list(set(array))
    mapping = dict(zip(unique_values, np.argsort(unique_values)))
    # apply mapping to our array
    # np.vectorize works similar map(), and can work with dictionaries
    array = np.vectorize(mapping.get)(array)
    return array

Hope that helps.