Changing ranges in timeline

Following this question I would like to change the X range (date), so that it will be from 1970, 1980,... till 2020 and the events will be a..b, etc... (I have a predefined list of events). I use the following code which dates starts with 1969 and ends with 1970 (instead of 1970 and 2020 respectively). The tried 2 options: 'event': ['a', 'b','c','d','e','f'], first option:

'date':pd.date_range(start='1970', periods=6)

second option:

'date': ['1970', '1980','1990','2000','2010','2020']

Here is the complete code:

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

df = pd.DataFrame(
    {
        'event': ['a', 'b','c','d','e','f'],
       'date': ['1970','1980','1990','2000','2010','2020']
     # ->   'date':pd.date_range(start='1970', periods=6)
             
    }
)

df['date'] = pd.to_datetime(df['date'])

levels = np.tile(
    [-5, 5, -3, 3, -1, 1],
    int(np.ceil(len(df)/6))
)[:len(df)]

fig, ax = plt.subplots(figsize=(12.8, 4), constrained_layout=True);
ax.set(title="A series of events")

ax.vlines(df['date'], 0, levels, color="tab:red");  # The vertical stems.
ax.plot(   # Baseline and markers on it.
    df['date'],
    np.zeros_like(df['date']),
    "-o",
    color="k",
    markerfacecolor="w"
);

# annotate lines
for d, l, r in zip(df['date'], levels, df['event']):
    ax.annotate(
        r,
        xy=(d, l),
        xytext=(-3, np.sign(l)*3),
        textcoords="offset points",
        horizontalalignment="right",
        verticalalignment="bottom" if l > 0 else "top"
    );

# format xaxis with 4 month intervals
ax.xaxis.set_major_locator(mdates.MonthLocator(interval=4));
ax.xaxis.set_major_formatter(mdates.DateFormatter("%b %Y"));
plt.setp(ax.get_xticklabels(), rotation=30, ha="right");

# remove y axis and spines
ax.yaxis.set_visible(False);
ax.yaxis.set_visible(False);
ax.spines["left"].set_visible(False)
ax.spines["top"].set_visible(False)
ax.spines["right"].set_visible(False)    
ax.margins(y=0.1);
plt.show();

As explained above I would like to see on Xais only years 1970 to 2020 (with no month and day) and respectively their events (a to f).

Solution

Answer based on comments and from what I've understood, see full code below (notice I have just added one line for year and commented out the xaxis part):


import matplotlib.pyplot as plt
import numpy as np
import matplotlib.dates as mdates
from datetime import datetime
import pandas as pd

df = pd.DataFrame(
    {
        'event': ['a', 'b','c','d','e','f'],
       'date': ['1970','1980','1990','2000','2010','2020']
     # ->   'date':pd.date_range(start='1970', periods=6)
             
    }
)

df['date'] = pd.to_datetime(df['date'])
df['date'] = df['date'].dt.year # ADDED THIS!

levels = np.tile(
    [-5, 5, -3, 3, -1, 1],
    int(np.ceil(len(df)/6))
)[:len(df)]

fig, ax = plt.subplots(figsize=(12.8, 4), constrained_layout=True);
ax.set(title="A series of events")

ax.vlines(df['date'], 0, levels, color="tab:red");  # The vertical stems.
ax.plot(   # Baseline and markers on it.
    df['date'],
    np.zeros_like(df['date']),
    "-o",
    color="k",
    markerfacecolor="w"
);

# annotate lines
for d, l, r in zip(df['date'], levels, df['event']):
    ax.annotate(
        r,
        xy=(d, l),
        xytext=(-3, np.sign(l)*3),
        textcoords="offset points",
        horizontalalignment="right",
        verticalalignment="bottom" if l > 0 else "top"
    );

# COMMENTED OUT THIS!
# format xaxis with 4 month intervals
# ax.xaxis.set_major_locator(mdates.MonthLocator(interval=4));
# ax.xaxis.set_major_formatter(mdates.DateFormatter("%b %Y"));
plt.setp(ax.get_xticklabels(), rotation=30, ha="right");

# remove y axis and spines
ax.yaxis.set_visible(False);
ax.yaxis.set_visible(False);
ax.spines["left"].set_visible(False)
ax.spines["top"].set_visible(False)
ax.spines["right"].set_visible(False)    
ax.margins(y=0.1);
plt.show();

OUTPUT: