http://guutaranoheya.web.fc2.com/math/matplotlib_ex.html
#!/usr/bin/env python
from pylab import *
x1 = arange(0, 2, 0.01)
y1 = sin(2*pi*x1)
y2 = sin(4*pi*x1) + 2
# reverse x and y2 so the polygon fills in order
x = concatenate( (x1,x1[::-1]) )
y = concatenate( (y1,y2[::-1]) )
p = fill(x, y, facecolor='g', alpha=0.5)
show()
