>>> """
==============
Scatter Masked
==============

Mask some data points and add a line demarking
masked regions.

"""
... import matplotlib.pyplot as plt
... import numpy as np
... 
... # Fixing random state for reproducibility
... np.random.seed(19680801)
... 
... 
... N = 100
... r0 = 0.6
... x = 0.9 * np.random.rand(N)
... y = 0.9 * np.random.rand(N)
... area = (20 * np.random.rand(N))**2  # 0 to 10 point radii
... c = np.sqrt(area)
... r = np.sqrt(x ** 2 + y ** 2)
... area1 = np.ma.masked_where(r < r0, area)
... area2 = np.ma.masked_where(r >= r0, area)
... plt.scatter(x, y, s=area1, marker='^', c=c)
... plt.scatter(x, y, s=area2, marker='o', c=c)
... # Show the boundary between the regions:
... theta = np.arange(0, np.pi / 2, 0.01)
... plt.plot(r0 * np.cos(theta), r0 * np.sin(theta))
... 
... plt.show()
...