Matplotlib plotting x ticks from Pandas DataFrame incorrectly

Question

I have a Pandas DataFrame containing 20 rows, indexed by datetime:

df.tail()
                     units       value
time        
2013-08-30T13:01:12  vehicles/h  662
2013-08-30T13:06:12  vehicles/h  701
2013-08-30T13:11:13  vehicles/h  477
2013-08-30T13:16:13  vehicles/h  179
2013-08-30T13:21:13  vehicles/h  576

I'm plotting it using matplotlib, like so:

ax = ls.plot(color='CC00CC')
# Only show hours and minutes
ax.set_xticklabels(
    [dt.strftime("%H:%M:%S") for dt in ls.index.to_datetime()])
plt.setp(ax.get_yticklabels(), fontsize=8)
ax.set_ylabel("Counts")
ax.set_xlabel("5-minute intervals on %s" % (datetime.datetime.today().strftime("%d/%m/%Y")))
plt.title("Vehicles")
plt.tight_layout()

Which results in the following plot:

enter image description here

But only the first few times are being shown as x ticks. The right-most x tick should be labelled 12:21:13, and some more of the intermediate ticks should be shown. What have I done wrong?

you probably have to explicitly set the x-tick locations. Just formatting them might not be enough to override the auto-scale/auto-placement of the ticks. — Schorsch
– Schorsch, Commented Aug 30, 2013 at 11:51
set_xlabel de-couples your label text from you data. It is dangerous and should only be used only occasionally. — tacaswell
– tacaswell, Commented Aug 30, 2013 at 18:06

urschrei · Accepted Answer · 2014-03-05 11:26:36Z

2

Turns out that I wasn't actually converting the time column to a DateTimeIndex properly. Doing that correctly fixed it:

Here's what my time column looked like:

df['time'][0]
>> u'2014-03-04T19:01:11'

Conversion like so:

# convert to DateTimeIndex, convert to UTC, and sort
df['time'] = pd.to_datetime(df['time'], format="%Y-%m-%dT%H:%M:%S")
df = df.set_index('time').tz_convert('UTC').sort()

edited Mar 5, 2014 at 11:26

answered Aug 30, 2013 at 12:52

urschrei

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3 Comments

Schorsch Over a year ago

Can you provide some more detail, please, for others in the same situation?

dranxo Over a year ago

Yeah I'm stuck on this right now to. The question/answer is not helping.

urschrei Over a year ago

@rcompton Added an example

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