Dear GSL-manual team,
the manual for the DHT should be updated:
when the scaling factor X is used,
the factor X^2 enters the calculation.
Then, DHT[f](k) calculates
1/(2Pi) int f(x) e^(-i x k) d^2x
for a two dimensional x.
This is not clear mentioned in the documentation.
Moreover, when using the factor X, after a forward and backward
transformation there enters the factor j_{nu,i}^2 / X^4, NOT only
j_{nu,i}^2.
This can easily be seen from the article of H.F. Johnson (mentioned in
the documentation), eq. (13), where DHT calculates always a term as
given by eq. (12), for forward and backward transform, respectively.
It took me some time to find this out, so it would be nice to update the
documentation with respect to future readership.
I am willing to help you, if it is not delayed by monthes.
Best regards,
Andreas