Dear developers,

I have a enhancement proposal: Could you please add the possibility to pass absolute values to axhline and axvline?

Background
I found it a bit inconvenient to draw horizontal or vertical lines to mark maxima or minima using the relative values if you are plotting actual data.

Code example

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
x = np.linspace(-1, 1)
def curve(x):
    return -np.random.rand()*(2)*x**2-np.random.rand() # the random numbers have just been introduced to avoid an easy guessing of the numbers in the following

fixed_curve = curve(x)
ax.plot(x, fixed_curve)
ylim = ax.get_ylim()
ytmp = (np.amax(fixed_curve) - ylim[0])/(ylim[1]-ylim[0])
ax.axvline(0, 0, ytmp) # better(?): ax.axvline(0, ylim[0], np.amax(fixed_curve), absolute = True)

Code explanation
In the example given above I want to mark to maximum with the coordinates (x, y) by a vertical line going from the maximum of the curve to the x axis to mark the value on the x axis. However, to exactly hit the maximum I first have to calculate the position of the maximum in respect the limits of the plot. Otherwise the line does either not "reach" the maximum or it "crosses" the maximum what would be counterintuitive.
This could be shortened by a parameter absolute or similar that allows you to draw a axvline or axhline from one absolute coordinate to another absolute coordinate.

What do you think about that suggestion?

Regards

Jakob