7

I have a question that sounds simple but it's driving me mad for some days. I have a historical time series closed in two lists: the first list is containing prices, let's say P = [1, 1.5, 1.3 ...] while the second list is containing the related dates, let's say D = [01/01/2010, 02/01/2010...]. What I would like to do is to plot SOME of these dates (when I say "some" is because the "best" result I got so far is to show all of them as tickers, so creating a black cloud of unreadable data in the x-axis) that, when you zoom in, are shown more in details. This picture is now having the progressive automated range made by Matplotlib:

Zoom-out

Instead of 0, 200, 400 etc. I would like to have the dates values that are related to the data-point plotted. Moreover, when I zoom-in I get the following:

Zoom-in

As well as I get the detail between 0 and 200 (20, 40 etc.) I would like to get the dates attached to the list. I'm sure this is a simple problem to solve but I'm new to Matplotlib as well as to Python and any hint would be appreciated. Thanks in advance

Improve this question

3 Answers 3

Reset to default
15

Matplotlib has sophisticated support for plotting dates. I'd recommend the use of AutoDateFormatter and AutoDateLocator. They are even locale-specific, so they choose month-names according to your locale.

import matplotlib.pyplot as plt
from matplotlib.dates import AutoDateFormatter, AutoDateLocator

xtick_locator = AutoDateLocator()
xtick_formatter = AutoDateFormatter(xtick_locator)

ax = plt.axes()
ax.xaxis.set_major_locator(xtick_locator)
ax.xaxis.set_major_formatter(xtick_formatter)

EDIT

For use with multiple subplots, use multiple locator/formatter pairs:

import datetime
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.dates import AutoDateFormatter, AutoDateLocator, date2num

x = [datetime.datetime.now() + datetime.timedelta(days=30*i) for i in range(20)]
y = np.random.random((20))

xtick_locator = AutoDateLocator()
xtick_formatter = AutoDateFormatter(xtick_locator)

for i in range(4):
    ax = plt.subplot(2,2,i+1)
    ax.xaxis.set_major_locator(xtick_locator)
    ax.xaxis.set_major_formatter(xtick_formatter)
    ax.plot(date2num(x),y)


plt.show()
Improve this answer
Sign up to request clarification or add additional context in comments.

4 Comments

Might this have any problem with the subplot? I have something like this: plt.figure(1) plt.subplot(211) plt.plot(P1) plt.subplot(212) plt.plot(P2) and the method you gave me is not working yet...
All methods that create subplots, like plt.axes, plt.subplot etc., return axes-objects. You have to create an individual locator / formatter pair for each of them and assign them to the axes-object.
Thanks, I'm trying to implement through it. However I'm still having the problem of not really readable dates. Cannot paste the picture in the comment here, but if you try to run your code I guess you will get my same result... any idea how to fix it?
You can use the minticks and maxticks parameters to AutoDateLocator to control the number oft ticks.
2

You can do timeseries plot with pandas For detail refer this : http://pandas.pydata.org/pandas-docs/dev/timeseries.html and http://pandas.pydata.org/pandas-docs/dev/generated/pandas.Series.plot.html

import pandas as pd    
DateStrList = ['01/01/2010','02/01/2010']
P = [2,3]
D = pd.Series([pd.to_datetime(date) for date in DateStrList])
series =pd.Series(P, index=D)
pd.Series.plot(series)
Improve this answer

1 Comment

Thanks a lot, I'm trying not to install additional libraries since the code is going to be use in several machines and no libraries distribution is expected to happen, but I will try it if I don't succeed with Thorsten method that is not assuming any additional reference.
1 
import matplotlib.pyplot as plt
import pandas
pandas.TimeSeries(P, index=D).plot()
plt.show()
Improve this answer

2 Comments

Could you insert some extra information, so your code would be easier to understand?
Thanks a lot, I'm trying not to install additional libraries since the code is going to be use in several machines and no libraries distribution is expected to happen, but I will try it if I don't succeed with Thorsten method that is not assuming any additional reference.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.