How to extract data from matplotlib plot


Question

I have a wxPython program which reads from different datasets, performs various types of simple on-the-fly analysis on the data and plots various combinations of the datasets to matplotlib canvas. I would like to have the opportunity to dump currently plotted data to file for more sophisticated analysis later on.

The question is: are there any methods in matplotlib that allow access to the data currently plotted in matplotlib.Figure?

1
16
1/20/2012 8:15:42 AM

Accepted Answer

Jakub is right about modifying the Python script to write out the data directly from the source from which it was sent into the plot; that's the way I'd prefer to do this. But for reference, if you do need to get data out of a plot, I think this should do it

gca().get_lines()[n].get_xydata()

Alternatively you can get the x and y data sets separately:

line = gca().get_lines()[n]
xd = line.get_xdata()
yd = line.get_ydata()
23
1/20/2012 9:12:36 AM

The matplotlib.pyplot.gca can be used to extract data from matplotlib plots. Here is a simple example:

import matplotlib.pyplot as plt
plt.plot([1,2,3],[4,5,6])
ax = plt.gca()
line = ax.lines[0]
line.get_xydata()

On running this, you will see 2 outputs - the plot and the data:

array([[1., 4.],
   [2., 5.],
   [3., 6.]])

enter image description here

You can also get the x data and y data seperately. On running line.get_xdata(), you will get:

array([1, 2, 3])

And on running line.get_ydata(), you will get:

array([4, 5, 6])

Note: gca stands for get current axis


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