Centering histogram bar plots

bins_array.py

"""Histogram bars are not centered at their label by default.
The function below returns the bins parameter value for use with matplotlib's 
hist() method.
"""

import numpy as np
import pandas as pd

def bin_array(distribution):
    """Returns an array to be used as the parameter value to center the
    histogram bars at the corresponding label.
    Arguments:
        distribution (np arr or pd series)
    
    Returns:
        bins (np arr)
    """
    uniq = distribution.unique()  # array of unique values
    uniq = uniq[~np.isnan(uniq)]  # remove nan values
    num_unique = len(uniq)
    uniq_min = min(uniq)
    bins = np.arange(uniq_min, num_unique + 1 + uniq_min) - 0.5
    return bins  # [0.5, 1.5, 2.5, 3.5] if there are 3 unique categories