Pandas graphing a timeseries, with vertical lines at selected dates
matplotlib, pandas, python
Solution
Thanks to @TomAugspurger
The solution is to get your axes back, and then use `ax.vlines`.
ax = cum_edits.plot()
ymin, ymax = ax.get_ylim()
ax.vlines(x=dates, ymin=ymin, ymax=ymax-1, color='r')
One last niggle is that if the vlines are `ymax` long, then matplotlib adds extra space to the top of my plot, so I just slightly reduce the length to be less than the original axes, that is why you see the `ymax=ymax-1`.
Problem
Consider this timeseries, the cumulative number of edits in a Wikipedia category. ``` In [555]: cum_edits.head() Out[555]: 2001-08-31 23:37:28 1 2001-09-01 05:09:28 2 2001-09-18 10:01:17 3 2001-10-27 06:52:45 4 2001-10-27 07:01:45 5 Name: edits, dtype: int64 In [565]: cum_edits.tail() Out[565]: 2014-01-29 16:05:15 53254 2014-01-29 16:07:09 53255 2014-01-29 16:11:43 53256 2014-01-29 18:09:44 53257 2014-01-29 18:12:09 53258 Name: edits, dtype: int64 ``` I have am to graph this like so: ``` In [567]: cum_edits.plot() Out[567]: <matplotlib.axes.AxesSubplot at 0x1359c810> ``` I would like to plot also vertical lines, after every `total_edits/n ; e.g. n=10` edits. I calculate these easily. ``` In [568]: dates Out[568]: [Timestamp('2006-06-04 04:46:22', tz=None), Timestamp('2007-01-28 23:53:02', tz=None), Timestamp('2007-09-16 10:52:02', tz=None), Timestamp('2008-04-28 21:20:40', tz=None), Timestamp('2009-04-12 22:07:13', tz=None), Timestamp('2010-04-09 18:45:37', tz=None), Timestamp('2011-03-28 23:38:12', tz=None), Timestamp('2012-05-24 13:44:35', tz=None), Timestamp('2013-03-05 17:57:29', tz=None), Timestamp('2014-01-29 16:05:15', tz=None)] ``` Normally one can use `axvline()` although I encounter two problems. Even if I call `plt.axvline(x=0.5, color='r')` just to produce an arbitrary line, I do not see it on top of the pandas plot. I am using IPython with `%pylab inline` by the way. And secondly, I do not now how to translate the dates into x position that are being used in `cum_edits.plot()` since the translation is invisible to me. Should I go about producing these vertical lines?