ConciseDateFormatter in subplots

Question

Using mdates.ConciseDateFormatter in multiple subplots gives erroneous offset in the axis:

import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates

dti = pd.to_datetime(["2016-08-31", "2016-09-30"])
ts0 = pd.DataFrame({"x": [0, 1]}, index=dti)
ts1 = pd.DataFrame({"x": [0, 1]}, index=dti + pd.Timedelta(365, "D"))
fig, axs = plt.subplots(2, 1, sharex=False)
ts0["x"].plot(ax=axs[0], marker="o")
ts1["x"].plot(ax=axs[1], marker="o")
dlocator = mdates.AutoDateLocator(minticks=6, maxticks=9)
axs[0].xaxis.set_major_locator(dlocator)
axs[0].xaxis.set_major_formatter(mdates.ConciseDateFormatter(dlocator))
axs[1].xaxis.set_major_locator(dlocator)
axs[1].xaxis.set_major_formatter(mdates.ConciseDateFormatter(dlocator))

The figure shows the x-axis tick labels for the top plot got messed up when assigning the major locator and formatter to the bottom plot. Is there any workaround to this bug or problem?

user_7758804 · Answer

It is required to instantiate AutoDateLocator for each axes
- See Formatting date ticks using ConciseDateFormatter
- As the plot axis is formatted, the locator object changes, as such, it can't be reused for the subsequent axes.
matplotlib.dates.ConciseDateFormatter
matplotlib.dates.AutoDateLocator
Tested in python 3.8.11, pandas 1.3.3, matplotlib 3.4.3

Plot Setup Code

fig, axs = plt.subplots(2, 1, sharex=False, figsize=(7, 7))
# axs = axs.flatten()  # required to easily index subplots, if subplots >= 2x2
ts0["x"].plot(ax=axs[0], marker="o")
ts1["x"].plot(ax=axs[1], marker="o")

Option 1

# instantiate AutoDateLocator
locator = mdates.AutoDateLocator(minticks=6, maxticks=9)
axs[0].xaxis.set_major_locator(locator)
axs[0].xaxis.set_major_formatter(mdates.ConciseDateFormatter(locator))

# instantiate AutoDateLocator
locator = mdates.AutoDateLocator(minticks=6, maxticks=9)
axs[1].xaxis.set_major_locator(locator)
axs[1].xaxis.set_major_formatter(mdates.ConciseDateFormatter(locator))

fig.tight_layout()

Option 2

for ax in axs:
    # instantiate AutoDateLocator
    locator = mdates.AutoDateLocator(minticks=6, maxticks=9)
    formatter = mdates.ConciseDateFormatter(locator)
    ax.xaxis.set_major_locator(locator)
    ax.xaxis.set_major_formatter(formatter)

fig.tight_layout()

ConciseDateFormatter in subplots

1 Answers

Plot Setup Code

Option 1

Option 2

Plot Result