How to do waffle charts in python? (square piechart)
I've put together a working example, below, which I think meets your needs. Some work is needed to fully generalize the approach, but I think you'll find that it's a good start. The trick was to use matshow() to solve your non-square problem, and to build a custom legend to easily account for categorical values.
import numpy as np
import pandas as pd
import matplotlib as mpl
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
# Let's make a default data frame with catagories and values.
df = pd.DataFrame({ 'catagories': ['cat1', 'cat2', 'cat3', 'cat4'],
'values': [84911, 14414, 10062, 8565] })
# Now, we define a desired height and width.
waffle_plot_width = 20
waffle_plot_height = 7
classes = df['catagories']
values = df['values']
def waffle_plot(classes, values, height, width, colormap):
# Compute the portion of the total assigned to each class.
class_portion = [float(v)/sum(values) for v in values]
# Compute the number of tiles for each catagories.
total_tiles = width * height
tiles_per_class = [round(p*total_tiles) for p in class_portion]
# Make a dummy matrix for use in plotting.
plot_matrix = np.zeros((height, width))
# Popoulate the dummy matrix with integer values.
class_index = 0
tile_index = 0
# Iterate over each tile.
for col in range(waffle_plot_width):
for row in range(height):
tile_index += 1
# If the number of tiles populated is sufficient for this class...
if tile_index > sum(tiles_per_class[0:class_index]):
# ...increment to the next class.
class_index += 1
# Set the class value to an integer, which increases with class.
plot_matrix[row, col] = class_index
# Create a new figure.
fig = plt.figure()
# Using matshow solves your "non-square" problem.
plt.matshow(plot_matrix, cmap=colormap)
plt.colorbar()
# Get the axis.
ax = plt.gca()
# Minor ticks
ax.set_xticks(np.arange(-.5, (width), 1), minor=True);
ax.set_yticks(np.arange(-.5, (height), 1), minor=True);
# Gridlines based on minor ticks
ax.grid(which='minor', color='w', linestyle='-', linewidth=2)
# Manually constructing a legend solves your "catagorical" problem.
legend_handles = []
for i, c in enumerate(classes):
lable_str = c + " (" + str(values[i]) + ")"
color_val = colormap(float(i+1)/len(classes))
legend_handles.append(mpatches.Patch(color=color_val, label=lable_str))
# Add the legend. Still a bit of work to do here, to perfect centering.
plt.legend(handles=legend_handles, loc=1, ncol=len(classes),
bbox_to_anchor=(0., -0.1, 0.95, .10))
plt.xticks([])
plt.yticks([])
# Call the plotting function.
waffle_plot(classes, values, waffle_plot_height, waffle_plot_width,
plt.cm.coolwarm)
Below is an example of the output this script produced. As you can see, it works fairly well for me, and meets all of your stated needs. Just let me know if it gives you any trouble. Enjoy!
I spent a few days to build a more general solution, PyWaffle.
You can install it through
pip install pywaffle
The source code: https://github.com/gyli/PyWaffle
PyWaffle does not use matshow() method, but builds those squares one by one. That makes it easier for customization. Besides, what it provides is a custom Figure class, which returns a figure object. By updating attributes of the figure, you can basically control everything in the chart.
Some examples:
Colored or transparent background:
import matplotlib.pyplot as plt
from pywaffle import Waffle
data = {'Democratic': 48, 'Republican': 46, 'Libertarian': 3}
fig = plt.figure(
FigureClass=Waffle,
rows=5,
values=data,
colors=("#983D3D", "#232066", "#DCB732"),
title={'label': 'Vote Percentage in 2016 US Presidential Election', 'loc': 'left'},
labels=["{0} ({1}%)".format(k, v) for k, v in data.items()],
legend={'loc': 'lower left', 'bbox_to_anchor': (0, -0.4), 'ncol': len(data), 'framealpha': 0}
)
fig.gca().set_facecolor('#EEEEEE')
fig.set_facecolor('#EEEEEE')
plt.show()
Use icons replacing squares:
data = {'Democratic': 48, 'Republican': 46, 'Libertarian': 3}
fig = plt.figure(
FigureClass=Waffle,
rows=5,
values=data,
colors=("#232066", "#983D3D", "#DCB732"),
legend={'loc': 'upper left', 'bbox_to_anchor': (1, 1)},
icons='child', icon_size=18,
icon_legend=True
)
Multiple subplots in one chart:
import pandas as pd
data = pd.DataFrame(
{
'labels': ['Hillary Clinton', 'Donald Trump', 'Others'],
'Virginia': [1981473, 1769443, 233715],
'Maryland': [1677928, 943169, 160349],
'West Virginia': [188794, 489371, 36258],
},
).set_index('labels')
fig = plt.figure(
FigureClass=Waffle,
plots={
'311': {
'values': data['Virginia'] / 30000,
'labels': ["{0} ({1})".format(n, v) for n, v in data['Virginia'].items()],
'legend': {'loc': 'upper left', 'bbox_to_anchor': (1.05, 1), 'fontsize': 8},
'title': {'label': '2016 Virginia Presidential Election Results', 'loc': 'left'}
},
'312': {
'values': data['Maryland'] / 30000,
'labels': ["{0} ({1})".format(n, v) for n, v in data['Maryland'].items()],
'legend': {'loc': 'upper left', 'bbox_to_anchor': (1.2, 1), 'fontsize': 8},
'title': {'label': '2016 Maryland Presidential Election Results', 'loc': 'left'}
},
'313': {
'values': data['West Virginia'] / 30000,
'labels': ["{0} ({1})".format(n, v) for n, v in data['West Virginia'].items()],
'legend': {'loc': 'upper left', 'bbox_to_anchor': (1.3, 1), 'fontsize': 8},
'title': {'label': '2016 West Virginia Presidential Election Results', 'loc': 'left'}
},
},
rows=5,
colors=("#2196f3", "#ff5252", "#999999"), # Default argument values for subplots
figsize=(9, 5) # figsize is a parameter of plt.figure
)
You can use this function for automatic creation of a waffle with simple parameters:
def create_waffle_chart(categories, values, height, width, colormap, value_sign=''):
# compute the proportion of each category with respect to the total
total_values = sum(values)
category_proportions = [(float(value) / total_values) for value in values]
# compute the total number of tiles
total_num_tiles = width * height # total number of tiles
print ('Total number of tiles is', total_num_tiles)
# compute the number of tiles for each catagory
tiles_per_category = [round(proportion * total_num_tiles) for proportion in category_proportions]
# print out number of tiles per category
for i, tiles in enumerate(tiles_per_category):
print (df_dsn.index.values[i] + ': ' + str(tiles))
# initialize the waffle chart as an empty matrix
waffle_chart = np.zeros((height, width))
# define indices to loop through waffle chart
category_index = 0
tile_index = 0
# populate the waffle chart
for col in range(width):
for row in range(height):
tile_index += 1
# if the number of tiles populated for the current category
# is equal to its corresponding allocated tiles...
if tile_index > sum(tiles_per_category[0:category_index]):
# ...proceed to the next category
category_index += 1
# set the class value to an integer, which increases with class
waffle_chart[row, col] = category_index
# instantiate a new figure object
fig = plt.figure()
# use matshow to display the waffle chart
colormap = plt.cm.coolwarm
plt.matshow(waffle_chart, cmap=colormap)
plt.colorbar()
# get the axis
ax = plt.gca()
# set minor ticks
ax.set_xticks(np.arange(-.5, (width), 1), minor=True)
ax.set_yticks(np.arange(-.5, (height), 1), minor=True)
# add dridlines based on minor ticks
ax.grid(which='minor', color='w', linestyle='-', linewidth=2)
plt.xticks([])
plt.yticks([])
# compute cumulative sum of individual categories to match color schemes between chart and legend
values_cumsum = np.cumsum(values)
total_values = values_cumsum[len(values_cumsum) - 1]
# create legend
legend_handles = []
for i, category in enumerate(categories):
if value_sign == '%':
label_str = category + ' (' + str(values[i]) + value_sign + ')'
else:
label_str = category + ' (' + value_sign + str(values[i]) + ')'
color_val = colormap(float(values_cumsum[i])/total_values)
legend_handles.append(mpatches.Patch(color=color_val, label=label_str))
# add legend to chart
plt.legend(
handles=legend_handles,
loc='lower center',
ncol=len(categories),
bbox_to_anchor=(0., -0.2, 0.95, .1)
)