"""
Histogram: a diagram consisting of rectangles whose area is proportional to the frequency
of a variable and whose width is equal to the class interval.

"""

from collections import Counter
from matplotlib import pyplot as plt

grades = [83, 95, 91, 87, 70, 0, 85, 82, 100, 67, 73, 77, 0]


def decile(grade: int) -> int:
    """Returns the decile the grade falls into.

    Floor division must be used.
    """

    return grade // 10 * 10


histogram = Counter(decile(grade) for grade in grades)

# Note We do not need to use the alignment tricks to center our bars
# That was a hold over from the previous Matplob lib API
plt.bar(x=histogram.keys(), height=histogram.values(), width=8)

# Used to set the axis scale x-min, x-max, y-min, y-max
# We want to fully show the x axis
# You usually always want your y to start at 0
plt.axis([-5, 105, 0, 5])

plt.xticks(range(0, 110, 10))
plt.xlabel("Decile")
plt.ylabel("# of Students")
plt.title("Distribution of Exam 1 Grades")
plt.show()