Plotting dates and associated values from a dictionary with Matplotlib

Question

I have a dictionary containing instances of Python's datetime.date and associated numeric values (integers). Something like this but a lot larger of course:

{datetime.date(2016, 5, 31): 27, datetime.date(2016, 9, 1): 87}

I am trying to use Matplotlib in order to build a line graph that would display these numeric values (y) against these dates (x), in chronological order.

Something like this:

I am new to Matplotlib and fairly new to Python as well. I tried a few solutions but they wouldn't add anything meaningful to the question.

Any help would be appreciated.

Thank you

juanpa.arrivillaga · Accepted Answer · 2016-09-15 21:28:27Z

5

Using only matplotlib:

In [1]: import matplotlib.pyplot as plt

In [2]: time_dict = {datetime.date(2016, 5, 31): 27, datetime.date(2016, 8, 1): 88, datetime.date(2016, 2, 5): 42,  datetime.date(2016, 9, 1): 87}

In [3]: x,y = zip(*sorted(time_dict.items()))

In [4]: plt.plot(x,y)
Out[4]: [<matplotlib.lines.Line2D at 0x7f460689ee48>]

This is the plot:

If you can use pandas, this task is also easy this way: relatively trivial:

In [6]: import pandas as pd

In [7]: df = pd.DataFrame.from_items([(k,[v]) for k,v in time_dict.items()], orient='index', columns=['values'])

In [8]: df
Out[8]: 
            values
2016-05-31      27
2016-09-01      87
2016-02-05      42
2016-08-01      88

In [9]: df.sort_index(inplace=True)

In [10]: df
Out[10]: 
            values
2016-02-05      42
2016-05-31      27
2016-08-01      88
2016-09-01      87

In [11]: df.plot()
Out[11]: <matplotlib.axes._subplots.AxesSubplot at 0x7f4611879160>

edited Sep 15, 2016 at 21:28

answered Sep 15, 2016 at 21:22

juanpa.arrivillaga

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1 Comment

adabsurdum Over a year ago

You could also use matplotlib's plot_date function: plt.plot_date(x,y,'-'). This helps with formatting the x axis.

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