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matplotlib.pyplot.axhline() in Python
  • Last Updated : 12 Apr, 2020

Matplotlib is a library in Python and it is numerical – mathematical extension for NumPy library. Pyplot is a state-based interface to a Matplotlib module which provides a MATLAB-like interface.

matplotlib.pyplot.axhline() Function

The axhline() function in pyplot module of matplotlib library is used to add a horizontal line across the axis.

Syntax: matplotlib.pyplot.axhline(y=0, xmin=0, xmax=1, **kwargs)

Parameters: This method accept the following parameters that are described below:

  • y: This parameter is an optional and it is position in data coordinates of the horizontal line.
  • xmin: This parameter is a scalar and optional. Its default value is 0.
  • xmax: This parameter is a scalar and optional. Its default value is 1.

Returns: This returns the following:

  • line : This returns the line created by this function.
  • Below examples illustrate the matplotlib.pyplot.axhline() function in matplotlib.pyplot:

    Example #1:

    # Implementation of matplotlib.pyplot.annotate() function
    import numpy as np
    import matplotlib.pyplot as plt
    t = np.linspace(-10, 10, 100)
    sig = 1 / t
    plt.axhline(y = 0, color ="green", linestyle ="--")
    plt.axhline(y = 0.5, color ="green", linestyle =":")
    plt.axhline(y = 1.0, color ="green", linestyle ="--")
    plt.axvline(color ="black")
    plt.plot(t, sig, linewidth = 2
             label = r"$\sigma(t) = \frac{1}{x}$")
    plt.xlim(-10, 10)
    plt.title("Graph of 1 / x")
    plt.legend(fontsize = 14)


    Example #2:

    # Implementation of matplotlib.pyplot.annotate() 
    # function
    import numpy as np
    import matplotlib.pyplot as plt
    x = np.linspace(0, 13, 100)
    plt.rcParams['lines.linewidth'] = 2
    plt.plot(x, np.sin(x), label ='Line1'
             color ='green', linestyle ="--")
    plt.plot(x, np.sin(x + 0.5), label ='Line2',
             color ='black', linestyle =":")
    plt.axhline(0, label ='Line3', color ='black')
    plt.title('Axhline() Example')
    l = plt.legend(loc ='upper right')
    # legend between blue and orange 
    # line


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