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"""
=============================
A pie and a donut with labels
=============================
Welcome to the Matplotlib bakery. We will create a pie and a donut
chart through the `pie method <matplotlib.axes.Axes.pie>` and
show how to label them with a `legend <matplotlib.axes.Axes.legend>`
as well as with `annotations <matplotlib.axes.Axes.annotate>`.
"""
# %%
# As usual we would start by defining the imports and create a figure with
# subplots.
# Now it's time for the pie. Starting with a pie recipe, we create the data
# and a list of labels from it.
#
# We can provide a function to the ``autopct`` argument, which will expand
# automatic percentage labeling by showing absolute values; we calculate
# the latter back from relative data and the known sum of all values.
#
# We then create the pie and store the returned objects for later. The first
# returned element of the returned tuple is a list of the wedges. Those are
# `matplotlib.patches.Wedge` patches, which can directly be used as the handles
# for a legend. We can use the legend's ``bbox_to_anchor`` argument to position
# the legend outside of the pie. Here we use the axes coordinates ``(1, 0, 0.5,
# 1)`` together with the location ``"center left"``; i.e. the left central
# point of the legend will be at the left central point of the bounding box,
# spanning from ``(1, 0)`` to ``(1.5, 1)`` in axes coordinates.
import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots(figsize=(6, 3), subplot_kw=dict(aspect="equal"))
recipe = ["375 g flour",
"75 g sugar",
"250 g butter",
"300 g berries"]
data = [float(x.split()[0]) for x in recipe]
ingredients = [x.split()[-1] for x in recipe]
def func(pct, allvals):
absolute = int(np.round(pct/100.*np.sum(allvals)))
return f"{pct:.1f}%\n({absolute:d} g)"
wedges, texts, autotexts = ax.pie(data, autopct=lambda pct: func(pct, data),
textprops=dict(color="w"))
ax.legend(wedges, ingredients,
title="Ingredients",
loc="center left",
bbox_to_anchor=(1, 0, 0.5, 1))
plt.setp(autotexts, size=8, weight="bold")
ax.set_title("Matplotlib bakery: A pie")
plt.show()
# %%
# Now it's time for the donut. Starting with a donut recipe, we transcribe
# the data to numbers (converting 1 egg to 50 g), and directly plot the pie.
# The pie? Wait... it's going to be donut, is it not?
# Well, as we see here, the donut is a pie, having a certain ``width`` set to
# the wedges, which is different from its radius. It's as easy as it gets.
# This is done via the ``wedgeprops`` argument.
#
# We then want to label the wedges via
# `annotations <matplotlib.axes.Axes.annotate>`. We first create some
# dictionaries of common properties, which we can later pass as keyword
# argument. We then iterate over all wedges and for each
#
# * calculate the angle of the wedge's center,
# * from that obtain the coordinates of the point at that angle on the
# circumference,
# * determine the horizontal alignment of the text, depending on which side
# of the circle the point lies,
# * update the connection style with the obtained angle to have the annotation
# arrow point outwards from the donut,
# * finally, create the annotation with all the previously
# determined parameters.
fig, ax = plt.subplots(figsize=(6, 3), subplot_kw=dict(aspect="equal"))
recipe = ["225 g flour",
"90 g sugar",
"1 egg",
"60 g butter",
"100 ml milk",
"1/2 package of yeast"]
data = [225, 90, 50, 60, 100, 5]
wedges, texts = ax.pie(data, wedgeprops=dict(width=0.5), startangle=-40)
bbox_props = dict(boxstyle="square,pad=0.3", fc="w", ec="k", lw=0.72)
kw = dict(arrowprops=dict(arrowstyle="-"),
bbox=bbox_props, zorder=0, va="center")
for i, p in enumerate(wedges):
ang = (p.theta2 - p.theta1)/2. + p.theta1
y = np.sin(np.deg2rad(ang))
x = np.cos(np.deg2rad(ang))
horizontalalignment = {-1: "right", 1: "left"}[int(np.sign(x))]
connectionstyle = f"angle,angleA=0,angleB={ang}"
kw["arrowprops"].update({"connectionstyle": connectionstyle})
ax.annotate(recipe[i], xy=(x, y), xytext=(1.35*np.sign(x), 1.4*y),
horizontalalignment=horizontalalignment, **kw)
ax.set_title("Matplotlib bakery: A donut")
plt.show()
# %%
# And here it is, the donut. Note however, that if we were to use this recipe,
# the ingredients would suffice for around 6 donuts - producing one huge
# donut is untested and might result in kitchen errors.
# %%
#
# .. admonition:: References
#
# The use of the following functions, methods, classes and modules is shown
# in this example:
#
# - `matplotlib.axes.Axes.pie` / `matplotlib.pyplot.pie`
# - `matplotlib.axes.Axes.legend` / `matplotlib.pyplot.legend`
#
# .. tags::
#
# component: label
# component: annotation
# plot-type: pie
# level: beginner
|
