Matplotlib & Python: assign a color when doing iterateive plotting

Question

I have a group of ellipses to plot, but the ellipses would be plotted in the same color. This makes it hard to differentiate one from another:

# import matplotlib as mpl
# from matplotlib import pyplot as plt

def plot_ellpises(ell_groups):
    print 'GMM Plot Result'
    fig, ax = plt.subplots()
    for ell in ell_groups:
        xy, width, height, angle = ell
        ell = mpl.patches.Ellipse(xy=xy, width=width, height=height, angle = angle)
        ell.set_alpha(0.5)
        ax.add_patch(ell)
    ax.autoscale()
    ax.set_aspect('equal')
    return plt.show() 

ell1= [-7.13529086, 5.28809598], 4.42823535, 5.97527801,107.60800706
ell2= [.96850139, 1.33792516], 5.73498868,8.98934084,97.8230716191
ell3= [1.43665497, 3.87692805], 1.42859078, 1.95525638,83.135072216
ell_groups = [ell1,ell2,ell3]
plot_ellpises(ell_groups)

I want to know how can I assign a color to each when plotting, so the ellpises would be easier to look at.

xnx · Accepted Answer · 2015-12-15 16:11:43Z

2

You can access Matplotlib's color-cycle with ax._get_lines.color_cycle. This is an iterator, so call next() on it each time you draw an ellipse:

def plot_ellpises(ell_groups):
    print 'GMM Plot Result'
    fig, ax = plt.subplots()
    colors = ax._get_lines.color_cycle
    for ell in ell_groups:
        xy, width, height, angle = ell
        ell = mpl.patches.Ellipse(xy=xy, width=width, height=height,
                                  angle = angle, facecolor=next(colors))
        ell.set_alpha(0.5)
        ax.add_patch(ell)
    ax.autoscale()
    ax.set_aspect('equal')
    return plt.show()

To specify the colors cycled through, you can set them explicitly as rcParams before plotting. e.g., for magenta, red, yellow:

mpl.rcParams['axes.color_cycle'] = ['m', 'r', 'y']

edited Dec 15, 2015 at 16:11

answered Dec 15, 2015 at 9:07

xnx

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3 Comments

ZK Zhao Over a year ago

This is much better than what I've thought. What I did is create a corlor_set = ['r','g','b'], and turn the iteration into for i, ell in enumerate(ell_group).

ZK Zhao Over a year ago

But, how can I change the color style? Mine is quite different from yours.

ZK Zhao Over a year ago

There is an additional question, what if I what to plot 4 intead of 3 ellpise? Then I need to add the additional color if I manually specified color set. I'm now thinking ax._get_lines.color_cycle may be a better option?

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