Alex Alex - 1 year ago 291
Python Question

In a matplotlib plot, can I highlight specific x-value ranges?

I'm making a visualization of historical stock data for a project, and I'd like to highlight regions of drops. For instance, when the stock is experiencing significant drawdown, I would like to highlight it with a red region.

Can I do this automatically, or will I have to draw a rectangle or something?

Answer Source

Have a look at axvspan (and axhspan for highlighting a region of the y-axis).

import matplotlib.pyplot as plt

plt.axvspan(3, 6, color='red', alpha=0.5)

enter image description here

If you're using dates, then you'll need to convert your min and max x values to matplotlib dates. Use matplotlib.dates.date2num for datetime objects or matplotlib.dates.datestr2num for various string timestamps.

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

t = mdates.drange(dt.datetime(2011, 10, 15), dt.datetime(2011, 11, 27),
y = np.sin(t)

fig, ax = plt.subplots()
ax.plot_date(t, y, 'b-')
ax.axvspan(*mdates.datestr2num(['10/27/2011', '11/2/2011']), color='red', alpha=0.5)

enter image description here

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