Matplotlib

Sun, 03 Sep 2023 00:00:00 +0000

Background

Matplotlib is a popular python package for figure plot and data visualization.

Installation

 pip install matplotlib

Submodules

Matplotlib comes with a series of submodules, e.g.,

matplotlib.pyplot is the counterpart of Matlab in matplotlib, which is essentially a collection of functions similar to Matlab.
matplotlib.pylab is a convenience module which imports matplotlib.pyplot (for plotting) and numpy (for array related operations) in a single name space.

General Concepts

In Matplotlib, there are some important concepts which can be illustrated below.

Concepts in a figure in Matplotlib (from https://matplotlib.org/1.5.1/faq/usage_faq.html)

A typical matplotlib Figure is comprised of a variety of components, as show below.

Components of a figure in Matplotlib (from https://matplotlib.org/stable/tutorials/introductory/usage.html)

`Figure`

A Figure object is essentially a canvas on which plot operations are performed. Clearly, it consists of one or more Axes objects.

 import matplotlib.pyplot as plt

 # Create an empty Figure object without any Axes.
 fig = plt.figure()
 fig = plt.figure(figsize=(WIDTH, HEIGHT), dpi=DPI)

 # Create a Figure object including one Axes.
 fig, ax = plt.subplots()

 # Create a Figure object including 2 x 3 Axes.
 fig, ax = plt.subplots(2, 3)

matplotlib.pyplot.gcf() can get the current Figure object.

`Axes`

Create Axes objects.
- matplotlib.pyplot.subplots
- figure.add_axes
A Axes object consists of a multiplicity Axis objects, e.g.,
- 2 Axis objects in a 2-dimension plot, e.g.., X-axis and Y-axis.
- 3 Axis objects in a 3-dimension plot, e.g.., X-axis, Y-axis, and Z-axis.
A Figure object's member function gca() can get the current Axes object.
A Figure object's member function subplots can create one or more Axes objects.
Member functions
- plot(X, Y)
- set_xlabel("XLABEL")
- set_ylabel("YLABEL")
- set_title("TITLE")
- set_xticks("XTICKS")
- set_yticks("YTICKS")
- set_xlim([XMIN, XMAX])
- set_ylim([YMIN, YMAX])
- legend()
- set_prop_cycle() : Set the random seed of colors, e.g., None for reset to the default.

`Axis`

Just as its name indicates, a Axis object defines the properties and attributes of a axis, e.g., limits, ticks, and ticklabels.

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