# investigate inherent noise in a Feff.dat file
# result: noise is at the 1.e-6 level, slightly worse than
# single precision, and consistent with the digitation in
# the Feff.dat file and linear interpolation
#
p1 = feffpath('feff0001.dat')
p1.e0 = 0
p1.sigma2 = 0.01 # 13
path2chi(p1)

# eps_off = 8.6e-6
sum = p1.chi    ## + 0* random.normal(size=len(p1.chi), scale=scale)
fdat = group(k=p1.k, chi=sum)
trans = feffit_transform(kmin=4, kmax=16, kweight=3, dk=8,
                         window='hanning', rmin=2., rmax=3.8)
d1 = feffit_dataset(data=fdat, pathlist=[p1], transform=trans)
d1.estimate_noise()
trans._xafsft(fdat.chi, group=fdat, rmax_out=32)
print( 'noise estimate k = ', d1.epsilon_k)
print( 'noise estimate r = ', d1.epsilon_r, log(d1.epsilon_r))
newplot(fdat.r, (fdat.chir_mag), xmax=30, win=1)
newplot(fdat.k, fdat.chi*fdat.k**2,  win=2)
   plot(fdat.k, fdat.kwin*2.0,  win=2)

newplot(fdat.r, log(fdat.chir_mag), xmax=30, win=3)