Adding an arrow below the x axis in R plots

I am trying to add arrows marking specific x coordinates below the x axis in an R plot. My x axis is at y=0 and when I try to use negative y-coordinates in arrows, so the arrows will be perpendicular …

Matplotlib autoscale

I need to get a plot that fits the data automatically using matplotlib. This is the code I was given:

import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection
….
lines = …

R – How to draw an empty plot?

Every once in a while I need to make an empty plot. This is the best could I come up with.

plot(0,xaxt=’n’,yaxt=’n’,bty=’n’,pch=”,ylab=”,xlab=”)
Any simpler solutions?

p.s 1: completely empty, …