replace numbers on X axis with dates when using line plot in matplotlib

Question

I am plotting a straight line plot with an array of numbers

fig, ax = plt.subplots()
ax.plot(x, 0 * x)

x is the array:

array([  0,1,2,3,4,5,6,7,8,9,10 ])

The line is fine but I want to display dates on the x axis.. I want to associate a date with each of the number and use those as my x ticks.

Can anyone suggest something?

possible duplicate of Plotting dates on the x-axis with Python's matplotlib — Jonathan Davies
– Jonathan Davies, Commented Feb 18, 2015 at 22:49

unutbu · Accepted Answer · 2015-02-19 11:50:40Z

2

You can control the ticker format of any value using a ticker.FuncFormatter:

import matplotlib.ticker as ticker
def todate(x, pos, today=DT.date.today()):
    return today+DT.timedelta(days=x)
fmt = ticker.FuncFormatter(todate)
ax.xaxis.set_major_formatter(fmt)

and if the dates appear too crowded, you can rotate them:

fig.autofmt_xdate(rotation=45)

For example,

import datetime as DT
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import matplotlib.ticker as ticker

x = np.array([0,1,2,3,4,5,6,7,8,9,10])

fig, ax = plt.subplots(figsize=(7, 4))
ax.plot(x, x**2*np.exp(-x))
def todate(x, pos, today=DT.date.today()):
    return today+DT.timedelta(days=x)
fmt = ticker.FuncFormatter(todate)
ax.xaxis.set_major_formatter(fmt)
fig.autofmt_xdate(rotation=45)  
plt.show()

yields

enter image description here

edited Feb 19, 2015 at 11:50

answered Feb 18, 2015 at 22:52

unutbu

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2 Comments

gaurav gurnani Over a year ago

Hey, thanks for the reply. But this is not what i want... i want my line to be plotted using numbers... i have to pass this line to a mpld3 plugin and it should be JSON serializable. I want to plot the line using my array x but display dates on the x ticks instead.. can you think of something ?

gaurav gurnani Over a year ago

My apologies.. this code worked.. I wasn't thinking straight. thank you

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