In R, there is a function called abline in which a line can be drawn on a plot based on the specification of the intercept (first argument) and the slope (second argument). For instance,

plot(1:10, 1:10)
abline(0, 1)

where the line with an intercept of 0 and the slope of 1 spans the entire range of the plot. Is there such a function in Matplotlib?

A lot of these solutions are focusing on adding a line to the plot that fits the data. Here's a simple solution for adding an arbitrary line to the plot based on a slope and intercept.

import matplotlib.pyplot as plt 
import numpy as np    

def abline(slope, intercept):
    """Plot a line from slope and intercept"""
    axes = plt.gca()
    x_vals = np.array(axes.get_xlim())
    y_vals = intercept + slope * x_vals
    plt.plot(x_vals, y_vals, '--')