Plot a horizontal line using matplotlib

Question

I have used spline interpolation to smooth a time series and would also like to add a horizontal line to the plot. But there seems to be an issue that is out of my grips. An

Answer 1

A nice and easy way for those people who always forget the command axhline is the following

plt.plot(x, [y]*len(x))

In your case xs = x and y = 40. If len(x) is large, then this becomes inefficient and you should really use axhline.