[FIXED] Show xtick labels on upper subplot with matplotlib

Issue

I feel like I've tried everything I've been able to find here, google, matplotlib documentation, and a couple of other forums. I can't get xticks to show on the upper subplot/graph, and the lower. I read in a forum related to matplotlib that others had the same problem as I, with earlier versions of matplotlib, but the thread died a couple of years ago, and the fixes that was suggested to work, didn't in my case.

The data is pulled from CSV files, and converted to floats, and datetime values

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import datetime as dt
import numpy as np

y = [26.0, 24.6, 23.9, 23.7, 23.6, 21.8, 22.0, 23.6]
x = [datetime.datetime(2020, 9, 2, 14, 13), datetime.datetime(2020, 9, 2, 14, 23), datetime.datetime(2020, 9, 2, 14, 33), datetime.datetime(2020, 9, 2, 14, 43), datetime.datetime(2020, 9, 2, 14, 53), datetime.datetime(2020, 9, 3, 0, 3), datetime.datetime(2020, 9, 4, 0, 3), datetime.datetime(2020, 9, 4, 0, 13)]
out = {datetime.date(2020, 9, 2): [26.0, 24.6, 23.9, 23.7, 23.6], datetime.date(2020, 9, 3): [21.8], datetime.date(2020, 9, 4): [21.6, 21.6]}

'''I found a thread a couple of days ago, where these 2 lines were the fix. honestly don't remember what the problem was, except it was related to datetime and plt'''
plt.gca().xaxis.set_major_formatter(mdates.DateFormatter('%d-%m-%Y %H:%M'))
plt.gca().xaxis.set_major_locator(mdates.DayLocator())

ax1 = plt.subplot(2, 1, 1)
plt.plot(x, y)
plt.xlabel('time')
plt.ylabel('temp')
plt.title('logs')
plt.grid()
ax1.xaxis.set_major_formatter(mdates.DateFormatter('%d-%m-%Y %H:%M'))

'''and also found how to subplot a boxplot from dict, from another thread'''
ax2 = plt.subplot(2, 1, 2)
labels, data = [*zip(*out.items())]  # 'transpose' items to parallel key, value lists
plt.boxplot(data)
plt.xticks(range(1, len(labels) + 1), labels)
plt.xlabel('date')
plt.ylabel('temp')

'''for rotating the xticklabels, and as far as I've been able to read, the most likely culprit'''
plt.gcf().autofmt_xdate()

plt.draw() # non-blocking call

plt.show() # keep last in script to keep windows open after execution

It might just be plt.gcf().autofmt_xdate() and if it is, is there a way to show xticklabels for both subplots, and still have them rotated?

Solution

As already pointed out by JohanC, you should use the matplotlib's object-oriented interface.

You can create the two subplots you need and then customize the axis based on your needs:

import matplotlib.pyplot as plt
import datetime as datetime
import matplotlib.dates as md


y = [26.0, 24.6, 23.9, 23.7, 23.6, 21.8, 22.0, 23.6]
x = [datetime.datetime(2020, 9, 2, 14, 13), datetime.datetime(2020, 9, 2, 14, 23), datetime.datetime(2020, 9, 2, 14, 33), datetime.datetime(2020, 9, 2, 14, 43), datetime.datetime(2020, 9, 2, 14, 53), datetime.datetime(2020, 9, 3, 0, 3), datetime.datetime(2020, 9, 4, 0, 3), datetime.datetime(2020, 9, 4, 0, 13)]
out = {datetime.date(2020, 9, 2): [26.0, 24.6, 23.9, 23.7, 23.6], datetime.date(2020, 9, 3): [21.8], datetime.date(2020, 9, 4): [21.6, 21.6]}

fig, ax = plt.subplots(2, 1)

ax[0].plot(x, y)
ax[0].set_xlabel('time')
ax[0].set_ylabel('temp')
ax[0].set_title('logs')
ax[0].grid()

labels, data = [*zip(*out.items())]
ax[1].boxplot(data)
ax[1].set_xticklabels([label.strftime('%Y-%m-%d') for label in labels])
ax[1].set_xlabel('date')
ax[1].set_ylabel('temp')

ax[0].xaxis.tick_top()
ax[0].xaxis.set_major_formatter(md.DateFormatter('%Y-%m-%d'))
ax[0].xaxis.set_major_locator(md.DayLocator())
plt.setp(ax[0].xaxis.get_majorticklabels(), rotation = 45)
ax[0].set_xlim(labels[0], labels[-1])

plt.setp(ax[1].xaxis.get_majorticklabels(), rotation = 45)

plt.show()

Side note: lower and upper labels are not perfectly aligned because you are trying to compare two different types of axis: to top upper one is continuous (between one tick and the next there are many other possible values for hours, minutes, seconds) while the lower one is categorical (you are plotting values for days only and between one thick and the next there are no others).

Answered By - Zephyr