Support plotting absolute times

[ddobie]

We're now starting to build proper timing solutions for ULPs, which means measuring pulse ToAs. This package is commonly used for doing this sort of work, but right now only supports plotting lightcurves/dynamic spectra with time relative to the observation start. This is quite annoying, because it means having to go back and figure out the observation start time.

It would be preferable to have a switch that allows users to plot absolute times (e.g. either MJD or ISOT).

I've started working on a PR that would do this, but it relies on astropy's time_support (https://docs.astropy.org/en/stable/visualization/matplotlib_integration.html#plotting-times). Unfortunately, as far as I can tell, this breaks when trying to use plt.imshow() and plt.errorbar(). I've raised an issue for that: astropy/astropy#17152

[ddobie]

@joshoewahp here is the code snippet I was playing with:

from matplotlib import pyplot as plt
from astropy.time import Time
from astropy.visualization import time_support

time_support()

plt.figure(figsize=(5,3))
plt.plot(Time([58000, 59000, 62000], format='mjd'), [1.2, 3.3, 2.3])


plt.figure(figsize=(5,3))
plt.errorbar(Time([58000, 59000, 62000], format='mjd'), [1.2, 3.3, 2.3])

data = [[1.2, 3.3, 2.3],[2.2, 4.3, 1.3],[2.4, 0.3, 3.3]]
times = Time([58000, 59000, 62000], format='mjd')

plt.figure(figsize=(5,3))
im = plt.imshow(
    data,
    extent=[times[0], times[-1], 0, 1],
    aspect="auto",
    origin="lower",
)

plt.show()