matplotlib string to dates

Question

Hi I am trying to convert a list of dates as strings to an x axis in matplotlib and I can't seem to get it to come out right.

dates =  ['2014-05-06', '2014-05-07', '2014-05-08', '2014-05-09', '2014-05-10', '2014-05-11', '2014-05-12', '2014-05-13']

import matplotlib
from matplotlib import pyplot
from matplotlib import dates

converted_dates = matplotlib.dates.datestr2num(dates)
x_axis = (converted_dates)

y_axis = range(0,8)
pyplot.plot( x_axis, y_axis, '-' )
pyplot.show()

This brings back 1 2 3 4 5 6 7 on the x axis on the chart, what am I missing. I would like this to display 2014-05-06 etc

This duplicates, e.g., stackoverflow.com/questions/3486121/… — cphlewis
– cphlewis, Commented May 14, 2014 at 1:05
maybe I am wrong but those are datetime objects and not strings. I am trying to convert strings to 2 date numbers — Trying_hard
– Trying_hard, Commented May 14, 2014 at 1:08
cgn has the answer, assuming that what you need is for the plot to compare and space the dates correctly? I'm confused by " I would like this to display 2014-05-06 etc" when that's what you have to start with. — cphlewis
– cphlewis, Commented May 14, 2014 at 1:22
@cphlewis Yes, but you can't plot against a list of strings, you can plot against a list of dates. — tacaswell
– tacaswell, Commented May 14, 2014 at 1:24

Azat Ibrakov · Accepted Answer · 2018-10-20 05:12:33Z

8

Is this the goal? (Threw in rotation because it almost always comes up, with dates.)

datelist =  ['2014-05-06', '2014-05-07', '2014-05-08', '2014-05-09', '2014-05-10',    '2014-05-11', '2014-05-12', '2014-05-13']

import matplotlib
from matplotlib import pyplot
from matplotlib import dates
import datetime

converted_dates = list(map(datetime.datetime.strptime, datelist, len(datelist)*['%Y-%m-%d']))
x_axis = converted_dates
formatter = dates.DateFormatter('%Y-%m-%d')


y_axis = range(0,8)
pyplot.plot( x_axis, y_axis, '-' )
ax = pyplot.gcf().axes[0] 
ax.xaxis.set_major_formatter(formatter)
pyplot.gcf().autofmt_xdate(rotation=25)
pyplot.show()

enter image description here

edited Oct 20, 2018 at 5:12

Azat Ibrakov

11.1k9 gold badges43 silver badges58 bronze badges

answered May 14, 2014 at 1:51

cphlewis

16.3k4 gold badges52 silver badges58 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

ImportanceOfBeingErnest · Accepted Answer · 2018-02-23 10:46:00Z

4

The idea of using matplotlib.dates.datestr2num is in principle correct. You would then need to tell matplotlib to actually interprete the resulting numbers as dates. One easy option is to use plot_date instead of plot.

import matplotlib
import matplotlib.pyplot as plt
import matplotlib.dates

dates =  ['2014-05-06', '2014-05-07', '2014-05-08', '2014-05-09', 
          '2014-05-10', '2014-05-11', '2014-05-12', '2014-05-13']

converted_dates = matplotlib.dates.datestr2num(dates)
x_axis = (converted_dates)

y_axis = range(0,8)
plt.plot_date( x_axis, y_axis, '-' )

plt.show()

answered Feb 23, 2018 at 10:46

ImportanceOfBeingErnest

342k61 gold badges737 silver badges771 bronze badges

Comments

cgnorthcutt · Accepted Answer · 2014-05-14 01:10:20Z

0

Try using strptime. Documentation is here: https://docs.python.org/2/library/datetime.html#strftime-strptime-behavior

For example:

import datetime
sDate = '2014-05-06'
dtDate = datetime.datetime.strptime(sDate,"%m-%d-%Y")

matplotlib can compare datetime objects.

answered May 14, 2014 at 1:10

cgnorthcutt

4,04636 silver badges44 bronze badges

2 Comments

cgnorthcutt Over a year ago

Also potential duplicate: stackoverflow.com/questions/12070193/…

tacaswell Over a year ago

That is not really a duplicate, it uses strptime, but the issue in that case is calling the wrong module, not issues with making it work

Jody Klymak · Accepted Answer · 2021-02-27 17:26:38Z

0

The easiest is to use numpy directly:


import matplotlib
from matplotlib import pyplot
from matplotlib import dates
import numpy as np

dates =  ['2014-05-06', '2014-05-07', '2014-05-08', '2014-05-09',
          '2014-05-10', '2014-05-11', '2014-05-12', '2014-05-13']

converted_dates = np.array(dates, dtype='datetime64[ms]')

ydata = range(0,8)
pyplot.plot(converted_dates, ydata, '-' )
pyplot.show()

answered Feb 27, 2021 at 17:26

Jody Klymak

6,1572 gold badges20 silver badges37 bronze badges

Collectives™ on Stack Overflow

matplotlib string to dates

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related