How to extract data from a pandas plot?

Question

I have a dataframe that I am plotting with pandas working in ipython. I am importing the usual stuff, then plotting the dataframe

import pandas as pd
import matplotlib.pyplot as plt
%matplotlib inline  

traydata_A[('x_TmId', 'Trays')].plot()
plt.xlabel('Hour of the day')
plt.ylabel('Number of picked/despatched trays')

and would like to get the actual data plotted by using (like e.g. in this question)

ax = plt.gca() 
line = ax.lines[0]

The end result is

  IndexError                                Traceback (most recent call last)
<ipython-input-220-d211b85302a5> in <module>()
      1 ax = plt.gca()
----> 2 line = ax.lines[0]

IndexError: list index out of range

what am I doing wrong? I am sure I have a deep misunderstanding of how pandas connects to matplotlib!

Why would you want to extract the data from the plot when you have it right available in the data frame you are plotting? — Jan Trienes, May 23 '17 at 08:23
In this particular case I could easily modify the dataframe itself. Let's assume it's something more complex as an histogram then. Yes it is a duplicate, but the answer does not work in my case. — famargar, May 23 '17 at 08:28

score 2 · Accepted Answer · edited Jun 20 '20 at 09:12

You will have to make sure to use the axes returned by the pandas plot function. In your code ax = plt.gca() returns a different axes than the one which is used by pandas. Either make sure to execute the code within the same context, or save the pandas axes into an intermediate variable. Full example:

s = pd.Series(data=[5850000, 6000000, 5700000, 13100000, 16331452], name='data')
ax = s.plot()
print(ax.get_lines()[0].get_xydata())
[[  0.00000000e+00   5.85000000e+06]
 [  1.00000000e+00   6.00000000e+06]
 [  2.00000000e+00   5.70000000e+06]
 [  3.00000000e+00   1.31000000e+07]
 [  4.00000000e+00   1.63314520e+07]]

From the documentation of matplotlib.pyplot.gca:

Get the current Axes instance on the current figure matching the given keyword args, or create one.

[...]

If the current axes doesn’t exist [..] the appropriate axes will be created and then returned.

How to extract data from a pandas plot?

1 Answers1