Re: [Matplotlib-users] fill area between two curves? fill_between?

[Andrew S. <str...@as...>]

On Sep 28, 2004, at 5:15 AM, John Hunter wrote:

>>>>>> "Dirk" ==   <rep...@we...> writes:
>
>     Dirk> I want to fill the area between two curves with a color
>     Dirk> (incl. alpha channel, I use the agg backend). fill() seems
>     Dirk> to fill only the area between the x-axis and one curve - at
>     Dirk> least I found no way for filling only the area between two
>     Dirk> graphs. Is there a way for doing so at all? Or do I have to
>     Dirk> 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

The fill() command itself does work if you give it coordinates for a 
closed polygon.  This draws a filled spiral:

from matplotlib.matlab import *
from numarray import *

theta = arange(0,8*pi,0.1)
a=1
b=.2

for dt in arange(0,2*pi,pi/2.0):

     x = a*cos( theta+dt )*exp(b*theta)
     y = a*sin( theta+dt )*exp(b*theta)

     dt = dt+pi/4.0

     x2 = a*cos( theta+dt )*exp(b*theta)
     y2 = a*sin( theta+dt )*exp(b*theta)

     xf = concatenate( (x,x2[::-1]) )
     yf = concatenate( (y,y2[::-1]) )

     p1=fill(xf,yf)

show()