Date tick locators and formatters#

import matplotlib.pyplot as plt
import numpy as np

# While these appear unused directly, they are used from eval'd strings.
from matplotlib.dates import (FR, MO, MONTHLY, SA, SU, TH, TU, WE, AutoDateFormatter,
                              AutoDateLocator, ConciseDateFormatter, DateFormatter,
                              DayLocator, HourLocator, MicrosecondLocator,
                              MinuteLocator, MonthLocator, RRuleLocator, SecondLocator,
                              WeekdayLocator, YearLocator, rrulewrapper)
import matplotlib.ticker as ticker


def plot_axis(ax, locator=None, xmax='2002-02-01', fmt=None, formatter=None):
    """Set up common parameters for the Axes in the example."""
    ax.spines[['left', 'right', 'top']].set_visible(False)
    ax.yaxis.set_major_locator(ticker.NullLocator())
    ax.tick_params(which='major', width=1.00, length=5)
    ax.tick_params(which='minor', width=0.75, length=2.5)
    ax.set_xlim(np.datetime64('2000-02-01'), np.datetime64(xmax))
    if locator:
        ax.xaxis.set_major_locator(eval(locator))
        ax.xaxis.set_major_formatter(DateFormatter(fmt))
    else:
        ax.xaxis.set_major_formatter(eval(formatter))
    ax.text(0.0, 0.2, locator or formatter, transform=ax.transAxes,
            fontsize=14, fontname='Monospace', color='tab:blue')

locators = [
    # locator as str, xmax, fmt
    ('AutoDateLocator(maxticks=8)', '2003-02-01', '%Y-%m'),
    ('YearLocator(month=4)', '2003-02-01', '%Y-%m'),
    ('MonthLocator(bymonth=[4, 8, 12])', '2003-02-01', '%Y-%m'),
    ('DayLocator(interval=180)', '2003-02-01', '%Y-%m-%d'),
    ('WeekdayLocator(byweekday=SU, interval=4)', '2000-07-01', '%a %Y-%m-%d'),
    ('HourLocator(byhour=range(0, 24, 6))', '2000-02-04', '%H h'),
    ('MinuteLocator(interval=15)', '2000-02-01 02:00', '%H:%M'),
    ('SecondLocator(bysecond=(0, 30))', '2000-02-01 00:02', '%H:%M:%S'),
    ('MicrosecondLocator(interval=1000)', '2000-02-01 00:00:00.005', '%S.%f'),
    ('RRuleLocator(rrulewrapper(freq=MONTHLY, \nbyweekday=(MO, TU, WE, TH, FR), '
     'bysetpos=-1))', '2000-07-01', '%Y-%m-%d'),
]

fig, axs = plt.subplots(len(locators), 1, figsize=(8, len(locators) * .8),
                        layout='constrained')
fig.suptitle('Date Locators')
for ax, (locator, xmax, fmt) in zip(axs, locators):
    plot_axis(ax, locator, xmax, fmt)

formatters = [
    'AutoDateFormatter(ax.xaxis.get_major_locator())',
    'ConciseDateFormatter(ax.xaxis.get_major_locator())',
    'DateFormatter("%b %Y")',
]

fig, axs = plt.subplots(len(formatters), 1, figsize=(8, len(formatters) * .8),
                        layout='constrained')
fig.suptitle('Date Formatters')
for ax, fmt in zip(axs, formatters):
    plot_axis(ax, formatter=fmt)