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How to customize matplotlib plots in Python

Banda Akshith

Introduction

  • Matplotlib is a graph-plotting, Python library that acts as a visualization library for the data.
  • It is an open-source library and is free to use for all types of metadata.
  • Matplotlib library is mostly used in Python, however, a few segments are written in C, C++, and JavaScript.

Installation of the Matplotlib Library

If you have python and pip! installed on your desktop, then you can install the Matplotlib library with ease.
Install the library using the command:

pip install matplotlib  

Once matplotlib is installed, you can import it in your executed or compiler using the following command:

import matplotlib

Now, matplotlib is imported and is ready to use.

To check the version of your matplotlib library, use the following command:

print(matplotlib.__version__)

Pyplot

Pyplot is a sub-module of matplotlib that is imported simultaneously with matplotlib. Usually, it is imported as plt:

import matplotlib.pyplot as plt

Now ,the pyplot package can be referred as plt.

Example
Let’s plot a graph using the matplotlib and pyplot package:

import matplotlib
import matplotlib.pyplot as plt
import numpy as np

xpoints=np.array([0,5])
ypoints=np.array([0,200])

plt.plot(xpoints,ypoints)
plt.show

Plotting on the graph

  • The plot() function is used to draw points(markers) on the graph.
  • By default, the plot function draws a line from one point to the another.
  • This function takes parameters for specifying points in the graph.
  • Two parameters are required, i.e., two arrays consisting of points for x-axis and y-axis.
#Positioning (2,4) and (10,10) on the graph
import matplotlib.pyplot as plt
import numpy as np

xpoints = np.array([2, 10])
ypoints = np.array([4, 10])

plt.plot(xpoints, ypoints)
plt.show()

Plotting without line

In order to plot a graph without a line:

  • You only plot the points, also known as markers, on the plane.
  • This can be done using string rotation parametersthey are basically dots (also notated as “o”).
#plotting two points on graph without joining
#let us take any two random points on the plane say (2,5) and (9,9)
import matplotlib.pyplot as plt
import numpy as np

xpoints = np.array([2, 9])
ypoints = np.array([5, 9])

plt.plot(xpoints, ypoints, 'o')
plt.show()

Various types of markers

Marker Description
o Dots
d Diamonds
* Stars
s Squares
p Pentagon
v Triangles
, Pixels
. Points
h Hexagon

These are some of the markers used. There are many more though.

#marking points on y-axis using the marker star.
import matplotlib.pyplot as plt
import numpy as np

ypoints = np.array([2, 4, 1, 8])

plt.plot(ypoints, marker = '*')
plt.show()

Marker size

You can also adjust the size of the markers with the ms command.
Let’s use the same example from above:

#marking points on y-axis using the marker star.
import matplotlib.pyplot as plt
import numpy as np

ypoints = np.array([2, 4, 1, 8])

plt.plot(ypoints, marker = '*',ms = 20)
plt.show()

Similarly, you can also change the marker outline and inside color using the mec and mfc commands.

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