Adding the same Patch instance to multiple subplots in matplotlib

Question

I am trying to add the same instance of a patch to multiple axes in matplotlib. Here is minimal example:

import matplotlib.pyplot as mpl_plt
import matplotlib.patches as mpl_patches

fig, (axes_1, axes_2) = mpl_plt.subplots(2,1)
axes_1.axis([-5, 5, -5, 5])
axes_2.axis([-5, 5, -5, 5])

# Create ellipse and add it to the axes
ellipse = mpl_patches.Ellipse((1,1), 0.5, 0.8)
axes_1.add_patch(ellipse)
axes_2.add_patch(ellipse)

# Change the position of the ellipse
ellipse.center = (2,2)

# Show the plot
mpl_plt.show()

In this example, the ellipse does not appear in either subplot. If I comment out the line axes_2.add_patch(ellipse), the ellipse appears in the first subplot at its moved location (2,2). Is it possible to have the ellipse appear in multiple axes and have changes to it reflected in both?

My end goal is being able to add artists to different subplots and have changes to the artists reflected in all axes. Even better would be to use zoomed_inset_axes from mpl_toolkits to have an inset plot that shows a close-up of a patch, where changes to the patch would be shown in both the main plot and the inset.

Do to the way the backend of matplotlib works you can not put the same patch instance in more than one axes. — tacaswell
– tacaswell, Commented Feb 7, 2014 at 22:41
Is there a simpler way to have the same patch in two subplots than to make two instances of the patch and then manually change the attribute of each instance every time a change (e.g., in position or colour) is needed? Seems like a lot of repeating yourself and extra memory. — kamek
– kamek, Commented Feb 10, 2014 at 15:23

Samwise · Accepted Answer · 2017-01-25 02:14:22Z

2

One way to do this is using a class to set all your custom settings for the artist. I've made an example class that has a default value for each property. If you then just make a reference to the art function of this class you get a new instance every time but with the exact same parameters. Notice how I changed Ellipse1 to have xy=(2,2) and that showed up on both plots. Just for an added flair, I made it so you could potentially call more than one patch type using getattr. This is assuming there are shared arguments for different patches or? You can make this as complicated or simple as you like I suppose.

import matplotlib.pyplot as mpl_plt
import matplotlib.patches as mpl_patches

class artist_instance:
    def __init__(self,
                 xy=None,
                 width=None,
                 height=None,
                 type=None,
                 ):
        self.xy=xy if xy is not None else (1,1)
        self.width=width if width is not None else 0.5
        self.height=height if height is not None else 0.8
        self.type=type if type is not None else 'Ellipse'

    def art(self):
        return getattr(mpl_patches,self.type)(xy=self.xy,width=self.width,height=self.height)

Ellipse1=artist_instance(xy=(2,2))

fig, (axes_1, axes_2) = mpl_plt.subplots(2,1)
axes_1.axis([-5, 5, -5, 5])
axes_2.axis([-5, 5, -5, 5])

axes_1.add_patch(Ellipse1.art())
axes_2.add_patch(Ellipse1.art())
mpl_plt.show()

Plot Result

answered Jan 25, 2017 at 2:14

Samwise

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2 Comments

kamek Over a year ago

Could you be more clear about how this answers the question? The goal is to be able to update attributes of the patch (e.g., its coordinates, color, width, etc.) AFTER its been added to the axes, and having those changes reflected in all the axes to which it was added. If you're method achieves this, could you be more explicit in your code snippet?

Samwise Over a year ago

You said you wanted changes to the artist reflected in all subplots. Since tacaswell said that you can't use the same artist in more than one subplot, my answer was a way to at least have all of the settings customized in one place which would make identical artists for each subplot. Can you not just make changes to the artist class as in my example and redraw?

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