Plotting timestamps in Python

Question

I am new to Python and am trying to create a simple line graph with time on the x axis and values on the y. I have a CSV file from which to import the data.

A sample of the data looks like this

I have tried to use the following code:

    import pandas as pd
    import numpy as np
    import matplotlib.pyplot as plt
    a_data = pd.read_csv("Data Sampler.csv")
    plt.plot(a_data.Timestamp, a_data.a)

However, I am receiving an error message: AttributeError: 'Series' object has no attribute 'find'

a_data.dtypes tells me that Timestamp is an object and A is float 64.

Can anyone help? From googling a solution, it looks like I need to convert the timestamp to a datetime within Python - however I am not having much luck with this (lots of error messages).

Thanks in advance.

wflynny · Accepted Answer · 2016-10-10 21:26:25Z

3

If you're using matplotlib.__version__ >= 1.5.0, then the following should work:

In [4]: df
Out[4]: 
          Timestamp         A
0  03/10/2016 16:00  0.033361
1  04/10/2016 16:01  0.123108
2  05/10/2016 16:02  0.021805

In [5]: df.index = pd.to_datetime(df.Timestamp, dayfirst=True)

In [6]: df
Out[6]: 
                            Timestamp         A
Timestamp                                      
2016-10-03 16:00:00  03/10/2016 16:00  0.033361
2016-10-04 16:01:00  04/10/2016 16:01  0.123108
2016-10-05 16:02:00  05/10/2016 16:02  0.021805

In [7]: plt.plot('A', data=df)
Out[7]: [<matplotlib.lines.Line2D at 0x7f8e3c0e8150>]

In [7]: plt.show()

Depending on the scale of your data, you can adjust the tick formatting of the x-axis using the appropriate tick formatters, see here for an example.

answered Oct 10, 2016 at 21:26

wflynny

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