[gmx-users] regarding on g_rotacf

[CHEN Pan]

Dear GROMACS Users,

I am confused on several flags for g_rotacf tool in GROMACS 4.6.4 version.

In the "help" information, it was written:

*g_rotacf -P 1 -nparm 2 -fft -n index -o rotacf-x-P1 -fa expfit-x-P1
-beginfit*
*2.5 -endfit 20.0*

but it seems that, "*-nparm*", "*-fft*" and "*-fa*" flags don't exist,
neither for GROMACS 5.0. Are these flags used in old version of GROMACS？

The obtained autocorrelation function can be further performed by FFT by
using xmgrace. Is there any other way that I can directly preform the *fft*
on an obtained rotational autocorrelation function, or indirectly by using
other GROMACS tools, such as g_dielectric for dipole autocorrelation
function?

Thanks for your help!

Best regards,
Pan