.. only:: html .. note:: :class: sphx-glr-download-link-note Click :ref:`here ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_statistics_barchart_demo.py: =================================== Percentiles as horizontal bar chart =================================== Bar charts are useful for visualizing counts, or summary statistics with error bars. Also see the :doc:`/gallery/lines_bars_and_markers/barchart` or the :doc:`/gallery/lines_bars_and_markers/barh` example for simpler versions of those features. This example comes from an application in which grade school gym teachers wanted to be able to show parents how their child did across a handful of fitness tests, and importantly, relative to how other children did. To extract the plotting code for demo purposes, we'll just make up some data for little Johnny Doe. .. code-block:: default 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() .. image:: /gallery/statistics/images/sphx_glr_barchart_demo_001.png :alt: Johnny Doe :class: sphx-glr-single-img ------------ References """""""""" The use of the following functions, methods and classes is shown in this example: .. code-block:: default matplotlib.axes.Axes.bar matplotlib.pyplot.bar matplotlib.axes.Axes.annotate matplotlib.pyplot.annotate matplotlib.axes.Axes.twinx .. rst-class:: sphx-glr-script-out Out: .. code-block:: none .. _sphx_glr_download_gallery_statistics_barchart_demo.py: .. only :: html .. container:: sphx-glr-footer :class: sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: barchart_demo.py ` .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: barchart_demo.ipynb ` .. only:: html .. rst-class:: sphx-glr-signature Keywords: matplotlib code example, codex, python plot, pyplot `Gallery generated by Sphinx-Gallery `_