Matplotlib | Stacked area charts and Stream graphs (stackplot)

Stacked area graphs are an extension of the basic area graph

The values of each group are displayed on top of each other, so you can see the sum of the values and their change on the same graph.

This article explains how to plot a stacked area chart in Python’s Matplotlib.

This article also explains how to plot ThemeRiver and stream graphs.

For basic area graphs, please refer to the following article

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Basic stacked area charts (Axes.stackplot)

Stacked area chart is drawn using the stackplot function

The following tabs explain the code and flowchart

import matplotlib.pyplot as plt
import numpy as np

# step1 Create dara
x = np.linspace(0, 10, 100)
dict_y = {
    'y1': x**1.5,
    'y2': x**2,
    'y3': x**2.1,
    'y4': np.exp(0.4*x),
    'y5': np.exp(0.4*x)+np.sin(x),
}
# step2 Create graph frames
fig, ax = plt.subplots()
# step3 Plot a stacked area chart
ax.stackplot(x, dict_y.values(), labels=dict_y.keys())

ax.set_xlabel('X label')
ax.set_ylabel('Y label')
ax.legend(loc='upper left')
ax.set_title('Simple Stackplot')

plt.show()

Symmetrical ThemeRiver centered on zero (sym)

If the stackplot function’s argument is baseline=sym, you can draw a stacked surface graph symmetric about zero.

It is a visualization method called ThemeRiver, a metaphor for a river

ax.axhline displays a straight line in the graph

# step3 plot a stacked area chart
ax.stackplot(x, dict_y.values(), labels=dict_y.keys(), baseline='sym')
ax.axhline(0, color='black', ls='--')

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Stream graph with minimal layer oscillation (wiggle)

If the argument to the stackplot function is baseline=wiggle, a stream graph is plotted

The stream graph is arranged to minimize layer “wobble” around the central axis

It is said to be easier to read than basic stacked surface graphs or ThemeRiver in value comparison work

# step3 Plot a area chart
ax.stackplot(x, dict_y.values(), labels=dict_y.keys(), baseline='wiggle')
ax.axhline(0, color='black', ls='--')

Colors of each group (colors)

The colors can be set for each group by defining colors as an argument to the stackplot function

In this article, the number of data is 5 elements, so I defined a list with 5 color names entered

Please refer to the following for possible color settings in Matplotlib

# step3 Plot a area chart
colors = ['forestgreen', 'limegreen', 'aquamarine', 'cyan', 'skyblue']
ax.stackplot(x, dict_y.values(), labels=dict_y.keys(), colors=colors)

References

Area-filled surface graph

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Matplotlib | Fill an area in a graph (fill_between, fill_betweenx) When plotting a graph in Python’s Matplotlib, have you ever wanted to fill in areas of the graph? This is often the case when you want to show a range or an …

Stacked area charts and stream graphs

stackplot function