How to extract data from matplotlib plot

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.]])

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

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()

Its Python, so you can modify the source script directly so the data is dumped before it is plotted

To sum up, for future reference:

If plotting with plt.plot() or plt.stem() or plt.step() you can get a list of Line2D objects with:

ax = plt.gca() # to get the axis
ax.get_lines()

For plt.pie(), plt.bar() or plt.barh() you can get a list of wedge or rectangle objects with:

ax = plt.gca() # to get the axis
ax.patches()

Then, depending on the situation you can get the data by running get_xdata(), get_ydata() (see Line2D) for more info.

or i.e get_height() for a bar plot (see Rectangle) for more info.

In general for all basic plotting functions, you can find what you are looking for by running ax.get_children()

that returns a list of the children Artists (the base class the includes all of the figure's elements).