I want to fill the area between two curves with a color

> (incl. alpha channel, I use the agg backend). fill() seems

> to fill only the area between the x-axis and one curve - at

> least I found no way for filling only the area between two

> graphs. Is there a way for doing so at all? Or do I have to

> use another graphic library for this kind of fill_between()?

All of the matplotlib plot commands create primitive objects

(lines.Line2D, patches.Rectangle, patches.Polygon, text.Text). If a

plot command doesn't suit your needs, you can roll your own by

creating the right kind of primitive object. Here is a fill_between

implementation

from matplotlib.matlab import *

from matplotlib.patches import Polygon

def fill_between(ax, x, y1, y2, **kwargs):

# add x,y2 in reverse order for proper polygon filling

verts = zip(x,y1) + [(x[i], y2[i]) for i in range(len(x)-1,-1,-1)]

poly = Polygon(verts, **kwargs)

ax.add_patch(poly)

ax.autoscale_view()

return poly

x = arange(0, 2, 0.01)

y1 = sin(2*pi*x)

y2 = sin(4*pi*x) + 2

ax = gca()

p = fill_between(ax, x, y1, y2, facecolor='g')

p.set_alpha(0.5)

show()

Hope this helps,

JDH