How do I change the range of the x-axis with datetime?


I’m trying to plot a graph of dates on the x-axis and values on the y-axis. It works fine, except that I can’t get the range of the x-axis to be appropriate. The x-axis range is always Jan 2012 to Jan 2016, despite my dates being from today. I am even specifying that xlim should be the first and last date.

I’m writing this for python-django, if that’s relevant.

 import datetime
 import matplotlib.pyplot as plt

 x = [, 1, 29),, 1, 29),, 1, 29)] 
 y = [2, 4, 1]

 fig, ax = plt.subplots()
 ax.plot_date(x, y)
 ax.set_xlim([x[0], x[-1]])

 canvas = FigureCanvas(plt.figure(1))
 response = HttpResponse(content_type='image/png')
 return response

And here is the output:
enter image description here

Asked By: aled1027




Having seen actual data from the OP, all of the values are at the same date/time. So matplotlib is automatically zooming the x-axis out. You can still manually set the x-axis limits with datetime objects

If I do something like this on matplotlib v1.3.1:

import datetime
import matplotlib.pyplot as plt

x = [, 1, 29)] * 3 
y = [2, 4, 1]

fig, ax = plt.subplots()
ax.plot_date(x, y, markerfacecolor='CornflowerBlue', markeredgecolor='white')
ax.set_xlim([, 1, 26),, 2, 1)])
ax.set_ylim([0, 5])

I get:

enter image description here

And the axes limits match the dates that I specified.

Answered By: Paul H

With help from Paul H’s solution, I was able to change the range of my time-based x-axis.

Here is a more general solution for other beginners.

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

# Set X range. Using left and right variables makes it easy to change the range.
left =, 3, 15)
right =, 7, 15)

# Create scatter plot of Positive Cases
  x, y, c="blue", edgecolor="black", 
  linewidths=1, marker = "o", alpha = 0.8, label="Total Positive Tested"

# Format the date into months & days

# Change the tick interval

# Puts x-axis labels on an angle
plt.gca().xaxis.set_tick_params(rotation = 30)  

# Changes x-axis range
plt.gca().set_xbound(left, right)

enter image description here

Answered By: Heather Claxton
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