gistfile1.txt

from numpy import loadtxt, log, abs, sign, exp
from scipy import polyfit
from pylab import plot, show

a = loadtxt("a.txt")
E = a[:, 0]
rt = a[:, 2]
E_f = E[-1]
E = E[:-1]
rt = rt[:-1]
S = sign(E - E_f)

x = rt
y = log(abs(E-E_f))
a, b = polyfit(x, y, 1)

E_est = E - S * exp(a*rt + b)

for c, d in zip(E, E_est):
    print c, d