Matplotlib for beginners
Matplotlib is a library for making 2D plots in Python. It is
designed with the philosophy that you should be able to
create simple plots with just a few commands:
1Initialize
import numpy as np
import matplotlib.pyplot as plt
2Prepare
X = np.linspace(0, 4*np.pi, 1000)
Y = np.sin(X)
3Render
fig, ax = plt.subplots()
ax.plot(X, Y)
fig.show()
4Observe
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Choose
Matplotlib offers several kind of plots (see Gallery):
X = np.random.uniform(0, 1, 100)
Y = np.random.uniform(0, 1, 100)
ax.scatter(X, Y)
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X = np.arange(10)
Y = np.random.uniform(1, 10, 10)
ax.bar(X, Y)
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Z = np.random.uniform(0, 1, (8,8)
ax.imshow(Z)
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Z = np.random.uniform(0, 1, (8,8)
ax.contourf(Z)
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Z = np.random.uniform(0, 1, 4)
ax.pie(Z)
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Z = np.random.normal(0, 1, 100)
ax.hist(Z)
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X = np.arange(5)
Y = np.random.uniform(0,1,5)
ax.errorbar(X, Y, Y/4)
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Z = np.random.normal(0,1,(100,3))
ax.boxplot(Z)
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Tweak
You can modify pretty much anything in a plot, including lim-
its, colors, markers, line width and styles, ticks and ticks la-
bels, titles, etc.
X = np.linspace(0,10,100)
Y = np.sin(X)
ax.plot(X, Y, color=”black”)
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X = np.linspace(0,10,100)
Y = np.sin(X)
ax.plot(X, Y, linestyle=”--”)
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X = np.linspace(0,10,100)
Y = np.sin(X)
ax.plot(X, Y, linewidth=5)
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X = np.linspace(0,10,100)
Y = np.sin(X)
ax.plot(X, Y, marker=”o”)
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Organize
You can plot several data on the the same figure but you can
also split a figure in several subplots (named Axes):
X = np.linspace(0,10,100)
Y1, Y1 = np.sin(X), np.cos(X)
ax.plot(X, Y1, Y2)
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fig, (ax1, ax2) = plt.subplots((2,1))
ax1.plot(X, Y1, color=”C1”)
ax2.plot(X, Y2, color=”C0”)
fig, (ax1, ax2) = plt.subplots((1,2))
ax1.plot(Y1, X, color=”C1”)
ax2.plot(Y2, X, color=”C0”)
Label (everything)
ax.plot(X, Y)
fig.suptitle(None)
ax.set_title(”A Sine wave”)
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A Sine wave
ax.plot(X, Y)
ax.set_ylabel(None)
ax.set_xlabel(”Time”)
Time
Explore
Figures are shown with a graphical user interface that all-
lows to zoom and pan the figure, to navigate between the
different views and to show the value under the mouse.
Save (bitmap or vector format)
fig.savefig(”my-first-figure.png”, dpi=300)
fig.savefig(”my-first-figure.pdf”)
Matplotlib 3.2 handout for beginners. Copyright (c) 2020 Nicolas P. Rougier. Released
under a CC-BY International 4.0 License. Supported by NumFocus Grant #12345.