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pythonmatplotlibgeometryscatter-plotscatter
Eric O. Lebigot
Eric O. Lebigot

Reputation: 94475

How to do a scatter plot with empty circles in Python?

In Python, with Matplotlib, how can a scatter plot with empty circles be plotted? The goal is to draw empty circles around some of the colored disks already plotted by scatter(), so as to highlight them, ideally without having to redraw the colored circles.

I tried facecolors=None, to no avail.

Upvotes: 271

Views: 506138

Answers (7)

aVral
aVral

Reputation: 133

In case you look for empty circle in the errorbar plot.

plt.errorbar(fmt='o', color='C0', mfc= "None")

Upvotes: 0

Aroc
Aroc

Reputation: 1263

Basend on the example of Gary Kerr and as proposed here one may create empty circles related to specified values with following code:

import matplotlib.pyplot as plt 
import numpy as np 
from matplotlib.markers import MarkerStyle

x = np.random.randn(60) 
y = np.random.randn(60)
z = np.random.randn(60)

g=plt.scatter(x, y, s=80, c=z)
g.set_facecolor('none')
plt.colorbar()
plt.show()

Upvotes: 9

Salvatore Cosentino
Salvatore Cosentino

Reputation: 7220

In matplotlib 2.0 there is a parameter called fillstyle which allows better control on the way markers are filled. In my case I have used it with errorbars but it works for markers in general http://matplotlib.org/api/_as_gen/matplotlib.axes.Axes.errorbar.html

fillstyle accepts the following values: [‘full’ | ‘left’ | ‘right’ | ‘bottom’ | ‘top’ | ‘none’]

There are two important things to keep in mind when using fillstyle,

1) If mfc is set to any kind of value it will take priority, hence, if you did set fillstyle to 'none' it would not take effect. So avoid using mfc in conjuntion with fillstyle

2) You might want to control the marker edge width (using markeredgewidth or mew) because if the marker is relatively small and the edge width is thick, the markers will look like filled even though they are not.

Following is an example using errorbars:

myplot.errorbar(x=myXval, y=myYval, yerr=myYerrVal, fmt='o', fillstyle='none', ecolor='blue',  mec='blue')

Upvotes: 6

Gary Kerr
Gary Kerr

Reputation: 14410

From the documentation for scatter:

Optional kwargs control the Collection properties; in particular:

    edgecolors:
        The string ‘none’ to plot faces with no outlines
    facecolors:
        The string ‘none’ to plot unfilled outlines

Try the following:

import matplotlib.pyplot as plt 
import numpy as np 

x = np.random.randn(60) 
y = np.random.randn(60)

plt.scatter(x, y, s=80, facecolors='none', edgecolors='r')
plt.show()

example image

Note: For other types of plots see this post on the use of markeredgecolor and markerfacecolor.

Upvotes: 398

Gökhan Sever
Gökhan Sever

Reputation: 8472

Would these work?

plt.scatter(np.random.randn(100), np.random.randn(100), facecolors='none')

example image

or using plot()

plt.plot(np.random.randn(100), np.random.randn(100), 'o', mfc='none')

example image

Upvotes: 104

denis
denis

Reputation: 21937

Here's another way: this adds a circle to the current axes, plot or image or whatever : 

from matplotlib.patches import Circle  # $matplotlib/patches.py

def circle( xy, radius, color="lightsteelblue", facecolor="none", alpha=1, ax=None ):
    """ add a circle to ax= or current axes
    """
        # from .../pylab_examples/ellipse_demo.py
    e = Circle( xy=xy, radius=radius )
    if ax is None:
        ax = pl.gca()  # ax = subplot( 1,1,1 )
    ax.add_artist(e)
    e.set_clip_box(ax.bbox)
    e.set_edgecolor( color )
    e.set_facecolor( facecolor )  # "none" not None
    e.set_alpha( alpha )

alt text

(The circles in the picture get squashed to ellipses because imshow aspect="auto" ).

Upvotes: 15

whatnick
whatnick

Reputation: 5470

So I assume you want to highlight some points that fit a certain criteria. You can use Prelude's command to do a second scatter plot of the hightlighted points with an empty circle and a first call to plot all the points. Make sure the s paramter is sufficiently small for the larger empty circles to enclose the smaller filled ones.

The other option is to not use scatter and draw the patches individually using the circle/ellipse command. These are in matplotlib.patches, here is some sample code on how to draw circles rectangles etc.

Upvotes: 1

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