Matplotlib is a popular python library used for plotting, It provides an object-oriented API to render GUI plots
Plotting a horizontal line is fairly simple, Using axhline()
The axhline() function in pyplot module of matplotlib library is used to add a horizontal line across the axis.
Syntax: matplotlib.pyplot.axhline(y, color, xmin, xmax, linestyle)
Parameters:
- y: Position on Y axis to plot the line, It accepts integers.
- xmin and xmax: scalar, optional, default: 0/1. It plots the line in the given range
- color: color for the line, It accepts a string. eg ‘r’ or ‘b’ .
- linestyle: Specifies the type of line, It accepts a string. eg ‘-‘, ‘–‘, ‘-.’, ‘:’, ‘None’, ‘ ‘, ”, ‘solid’, ‘dashed’, ‘dashdot’, ‘dotted’
Plotting a single horizontal line
Python3
# importing libraryimport matplotlib.pyplot as plt # specifying horizontal line typeplt.axhline(y = 0.5, color = 'r', linestyle = '-') # rendering the plotplt.show() |
Output:
Plotting multiple horizontal lines
To plot multiple horizontal lines, use the axhline() method multiple times.
Python
# importing the moduleimport matplotlib.pyplot as plt # plotting line within the given rangeplt.axhline(y = .5, xmin = 0.25, xmax = 0.9) # line colour is blueplt.axhline(y = 3, color = 'b', linestyle = ':') # line colour is whiteplt.axhline(y = 1, color = 'w', linestyle = '--') # line colour is redplt.axhline(y = 2, color = 'r', linestyle = 'dashed') # adding axis labels plt.xlabel('x - axis')plt.ylabel('y - axis') # displaying the plotplt.show() |
Output:
Adding the legend
The legend can be added using the legend() function.
Python3
# importing the moduleimport matplotlib.pyplot as plt # plotting line within the given rangeplt.axhline(y = .5, xmin = 0.25, xmax = 0.9) # line colour is blueplt.axhline(y = 3, color = 'b', linestyle = ':', label = "blue line") # line colour is whiteplt.axhline(y = 1, color = 'w', linestyle = '--', label = "white line") # line colour is redplt.axhline(y = 2, color = 'r', linestyle = 'dashed', label = "red line") # adding axis labels plt.xlabel('x - axis')plt.ylabel('y - axis') # plotting the legendplt.legend(bbox_to_anchor = (1.0, 1), loc = 'upper center') # displaying the plotplt.show() |
Output:
