Matplotlib: Line plot with markers

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Methods to draw line plot with markers with the help of Matplotlib

In this article, we will discuss some basics of matplotlib and then discuss how to draw line plots with markers.

Matplotlib

We know that data that is in the form of numbers is difficult and boring to analyze. But if we convert that number into graphs, bar plots, piecharts, etc then it will be easy and interesting to visualize the data. Here Matplotlib library of python came into use. Matplotlib is a comprehensive library for creating static, animated, and interactive visualizations in Python.

For using this library we have to first import it into the program. For importing this we can use

from matplotlib import pyplot as plt or import matplotlib. pyplot as plt.

In this article, we only discuss the line plot. So let see the function in matplotlib to draw a line plot.

syntax:  plt.plot(x,y, scalex=True, scaley=True, data=None, marker=’marker style’, **kwargs)

Parameters

  1. x,y: They represent vertical and horizontal axis.
  2. scalex, scaley: These parameters determine if the view limits are adapted to the data limits. The default value is True.
  3. marker: It contains types of markers that can be used. Like point marker, circle marker, etc.

Here is the list of markers used in this

  • “’.’“           point marker
  • “’,’“           pixel marker
  • “’o’“          circle marker
  • “’v’“          triangle_down marker
  • “’^’“          triangle_up marker
  • “'<‘“          triangle_left marker
  • “’>’“          triangle_right marker
  • “’1’“          tri_down marker
  • “’2’“          tri_up marker
  • “’3’“          tri_left marker
  • “’4’“          tri_right marker
  • “’s’“          square marker
  • “’p’“          pentagon marker
  • “’*’“          star marker
  • “’h’“          hexagon1 marker
  • “’H’“         hexagon2 marker
  • “’+’“          plus marker
  • “’x’“          x marker
  • “’D’“         diamond marker
  • “’d’“          thin_diamond marker
  • “’|’“           vline marker
  • “’_’“          hline marker

Examples of Line plot with markers in matplotlib

  • Line Plot with the Point marker

Here we use marker='.'.Let see this with the help of an example.

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(-5,40,.5)
y = np.sin(x)
plt.plot(x,y, marker='.')
plt.title('Sin Function')
plt.xlabel('x values')
plt.ylabel('y= sin(x)')
plt.show()

Output

  • Line Plot with the Point marker and give marker some color

In the above example, we see the color of the marker is the same as the color of the line plot. So there is an attribute in plt.plot() function marker face color or mfc: color which is used to give color to the marker. Let see this with the help of an example.

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(-5,40,.5)
y = np.sin(x)
plt.plot(x,y, marker='.',mfc='red')
plt.title('Sin Function')
plt.xlabel('x values')
plt.ylabel('y= sin(x)')
plt.show()

Output

Here we see that color of the pointer changes to red.

  • Line Plot with the Point marker and change the size of the marker

To change the size of the marker there is an attribute in pointer ply.plot() function that is used to achieve this. marker size or ms attribute is used to achieve this. We can pass an int value in ms and then its size increases or decreases according to this. Let see this with the help of an example.

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(-5,40,.5)
y = np.sin(x)
plt.plot(x,y, marker='.',mfc='red',ms='17')
plt.title('Sin Function')
plt.xlabel('x values')
plt.ylabel('y= sin(x)')
plt.show()

Output

Here we see that size of the pointer changes.

  • Line Plot with the Point marker and change the color of the edge of the marker

We can also change the color of the edge of marker with the help of markeredgecolor or mec attribute. Let see this with the help of an example.

import matplotlib.pyplot as plt
import numpy as np

x = np.arange(-5,40,.5)
y = np.sin(x)
plt.plot(x,y, marker='.',mfc='red',ms='17', mec='yellow')
plt.title('Sin Function')
plt.xlabel('x values')
plt.ylabel('y= sin(x)')
plt.show()

Output

Here we see that the color of the edge of the pointer changes to yellow.

So here are some examples of how we can work with markers in line plots.

Note: These examples are applicable to any of the marker.