from pylab import *
def Horton(t):
    fu = 3.0
    f0 = 12.0
    k = 0.5
    H = fu+(f0-fu)*exp(-k*t)
    return H
t = arange(0.0, 60.0, 0.5)
plot(t, Horton(t))
ytext = ylabel('Infiltrationsrate (mm/min)')
xtext = xlabel('Zeit (Min.)')
show()