demo01_matplotlibBarchart.py

import numpy as np
import matplotlib
import matplotlib.pyplot as plt
from matplotlib.ticker import MaxNLocator
from collections import namedtuple

np.random.seed(42)

Student = namedtuple('Student', ['name', 'grade', 'gender'])
Score = namedtuple('Score', ['score', 'percentile'])

# GLOBAL CONSTANTS
test_names = ['Pacer Test', 'Flexed Arm\n Hang', 'Mile Run', 'Agility',
              'Push Ups']
test_units = dict(zip(test_names, ['laps', 'sec', 'min:sec', 'sec', '']))


def attach_ordinal(num):
    """Convert an integer to an ordinal string, e.g. 2 -> '2nd'."""
    suffixes = {str(i): v
                for i, v in enumerate(['th', 'st', 'nd', 'rd', 'th',
                                       'th', 'th', 'th', 'th', 'th'])}
    v = str(num)
    # special case early teens
    if v in {'11', '12', '13'}:
        return v + 'th'
    return v + suffixes[v[-1]]


def format_score(score, test):
    """
    Create score labels for the right y-axis as the test name followed by the
    measurement unit (if any), split over two lines.
    """
    unit = test_units[test]
    if unit:
        return f'{score}\n{unit}'
    else:  # If no unit, don't include a newline, so that label stays centered.
        return score


def format_ycursor(y):
    y = int(y)
    if y < 0 or y >= len(test_names):
        return ''
    else:
        return test_names[y]


def plot_student_results(student, scores, cohort_size):
    fig, ax1 = plt.subplots(figsize=(9, 7))  # Create the figure
    fig.subplots_adjust(left=0.115, right=0.88)
    fig.canvas.set_window_title('Eldorado K-8 Fitness Chart')

    pos = np.arange(len(test_names))

    rects = ax1.barh(pos, [scores[k].percentile for k in test_names],
                     align='center',
                     height=0.5,
                     tick_label=test_names)

    ax1.set_title(student.name)

    ax1.set_xlim([0, 100])
    ax1.xaxis.set_major_locator(MaxNLocator(11))
    ax1.xaxis.grid(True, linestyle='--', which='major',
                   color='grey', alpha=.25)

    # Plot a solid vertical gridline to highlight the median position
    ax1.axvline(50, color='grey', alpha=0.25)

    # Set the right-hand Y-axis ticks and labels
    ax2 = ax1.twinx()

    # Set the tick locations
    ax2.set_yticks(pos)
    # Set equal limits on both yaxis so that the ticks line up
    ax2.set_ylim(ax1.get_ylim())

    # Set the tick labels
    ax2.set_yticklabels([format_score(scores[k].score, k) for k in test_names])

    ax2.set_ylabel('Test Scores')

    xlabel = ('Percentile Ranking Across {grade} Grade {gender}s\n'
              'Cohort Size: {cohort_size}')
    ax1.set_xlabel(xlabel.format(grade=attach_ordinal(student.grade),
                                 gender=student.gender.title(),
                                 cohort_size=cohort_size))

    rect_labels = []
    # Lastly, write in the ranking inside each bar to aid in interpretation
    for rect in rects:
        # Rectangle widths are already integer-valued but are floating
        # type, so it helps to remove the trailing decimal point and 0 by
        # converting width to int type
        width = int(rect.get_width())

        rank_str = attach_ordinal(width)
        # The bars aren't wide enough to print the ranking inside
        if width < 40:
            # Shift the text to the right side of the right edge
            xloc = 5
            # Black against white background
            clr = 'black'
            align = 'left'
        else:
            # Shift the text to the left side of the right edge
            xloc = -5
            # White on magenta
            clr = 'white'
            align = 'right'

        # Center the text vertically in the bar
        yloc = rect.get_y() + rect.get_height() / 2
        label = ax1.annotate(
            rank_str, xy=(width, yloc), xytext=(xloc, 0),
            textcoords="offset points",
            horizontalalignment=align, verticalalignment='center',
            color=clr, weight='bold', clip_on=True)
        rect_labels.append(label)

    # Make the interactive mouse over give the bar title
    ax2.fmt_ydata = format_ycursor
    # Return all of the artists created
    return {'fig': fig,
            'ax': ax1,
            'ax_right': ax2,
            'bars': rects,
            'perc_labels': rect_labels}


student = Student('Johnny Doe', 2, 'boy')
scores = dict(zip(
    test_names,
    (Score(v, p) for v, p in
     zip(['7', '48', '12:52', '17', '14'],
         np.round(np.random.uniform(0, 100, len(test_names)), 0)))))
cohort_size = 62  # The number of other 2nd grade boys

arts = plot_student_results(student, scores, cohort_size)
plt.show()