Comparing to Mantid PDFFourierTransform

[rosswhitfield]

I used this script to compare the Fourier transform algorithm PDFFourierTransform of Mantid and pystog.

from mantid.simpleapi import CreateWorkspace, PDFFourierTransform
import numpy as np
from pystog import Transformer
transformer = Transformer()

xx = np.arange(0, 10, 0.1)
yy = np.exp(-(2.0 * xx)**2)
ws = CreateWorkspace(DataX=xx, DataY=yy, DataE=yy, UnitX='MomentumTransfer')
Rt = PDFFourierTransform(ws, InputSofQType='Q[S(Q)-1]', PDFType='G(r)')

y = Rt.extractY()[0]
x = Rt.extractX()[0]
e = Rt.extractE()[0]

r, gr, dgr = transformer.F_to_G(xx, yy, x, yy)

After c80d57b this shows that you get the same G(r) (comparing y and gr) and delta-G(r) (comparing e and dgr).

But if you change the input q to not start at 0 (xx=np.arange(0.1,10,0.1)) then the results differ.