Matplotlib fill between multiple lines

Question

I would like to fill between 3 lines in matplotlib.pyplot but unfortunately the fill_between gives me opportunity to fill between only two lines. Any ideas how to deal with this?

Edit:

Ok, I did not explain what I really mean since I cannot add the picture with my current reputation so maybe in that way:

I try to fill the polygon bounded by these lines and I have no idea how because fill_between gives me opportunity to fill only area between two of them. Below the fill equation:

y <= 4- 2x y <= 3 - 1/2x y <= 1 - x y >= 0 x >= 0 

the x and y bigger than 0 is obvious. I start the plot from (0,0) but I still have 3 lines...

y <= 4- 2x y <= 3 - 1/2x y <= 1 - x 

Answer 1

If you start the plot in point (0, 0), and therefore do not need to consider the area of the polygon not in the first quadrant, then this should do the trick in this particular situation:

import matplotlib.pyplot as plt import numpy as np  x = np.arange(0,10,0.1)  # The lines to plot y1 = 4 - 2*x y2 = 3 - 0.5*x y3 = 1 -x  # The upper edge of polygon (min of lines y1 & y2) y4 = np.minimum(y1, y2)  # Set y-limit, making neg y-values not show in plot plt.ylim(0, 5)  # Plotting of lines plt.plot(x, y1,          x, y2,          x, y3)  # Filling between line y3 and line y4 plt.fill_between(x, y3, y4, color='grey', alpha='0.5') plt.show() 

Answer 2

To use fill_between, specify the X values first, than the two Y sets that you want to "fill between". An example is show below:

import pylab as plt import numpy as np  X  = np.linspace(0,3,200) Y1 = X**2 + 3 Y2 = np.exp(X) + 2 Y3 = np.cos(X)  plt.plot(X,Y1,lw=4) plt.plot(X,Y2,lw=4) plt.plot(X,Y3,lw=4)  plt.fill_between(X, Y1,Y2,color='k',alpha=.5) plt.fill_between(X, Y1,Y3,color='y',alpha=.5)  plt.show() 

If, instead, you only wanted to fill between Y2 and Y3:

plt.fill_between(X, Y2,Y3,color='m',alpha=.5) 

this would give you