How to Convert Dates to a Numerical Format for Plotting?

Converting Dates to Numerical Format for Plotting

Plotting data against dates can be challenging when the dates are stored in a different format, such as "01/02/1991." This article provides a solution for converting dates into a numerical format that can be easily plotted on the x-axis.

As mentioned in the question, converting the dates using strftime('%Y%m%d') alone may not be sufficient. To resolve this issue, consider using Python's datetime module to convert the strings to instances of datetime.date.

<code class="python">import datetime as dt

dates = ['01/02/1991','01/03/1991','01/04/1991']
x = [dt.datetime.strptime(d,'%m/%d/%Y').date() for d in dates]</code>

With the dates converted to datetime.date objects, we can proceed to plot using matplotlib.pyplot, as demonstrated in the solution provided.

<code class="python">import matplotlib.pyplot as plt
import matplotlib.dates as mdates

plt.gca().xaxis.set_major_formatter(mdates.DateFormatter('%m/%d/%Y'))
plt.gca().xaxis.set_major_locator(mdates.DayLocator())
plt.plot(x,y)
plt.gcf().autofmt_xdate()</code>

By following these steps, you can successfully plot data against dates, even when the dates are stored in a non-numerical format.

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