I think you're slightly confused as to exactly how matplotlib handles times and dates behind the scenes.
All datetimes in matplotlib are represented as simple floats. 1 day corresponds to a difference of 1.0, and the dates are in days since 1900 (if I remember correctly, anyway).
So, in order to plot just the time of a given date, you need to use a % 1
.
I'm going to use points, but you can easily use bars. Look into using the bottom
keyword argument if you do use plt.bar
, so that the bottom of the bars will start at the start time of your intervals (and remember that the second argument is the height of the bar, not its top y-value).
For example:
import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
import datetime as dt
# Make a series of events 1 day apart
x = mpl.dates.drange(dt.datetime(2009,10,1),
dt.datetime(2010,1,15),
dt.timedelta(days=1))
# Vary the datetimes so that they occur at random times
# Remember, 1.0 is equivalent to 1 day in this case...
x += np.random.random(x.size)
# We can extract the time by using a modulo 1, and adding an arbitrary base date
times = x % 1 + int(x[0]) # (The int is so the y-axis starts at midnight...)
# I'm just plotting points here, but you could just as easily use a bar.
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot_date(x, times, 'ro')
ax.yaxis_date()
fig.autofmt_xdate()
plt.show()
Hopefully that helps a bit!
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