[gmx-users] g_angle - Order of Legendre polynomial for ACF - BUG ?

[David van der Spoel]

Dennis Glass wrote:
> 
> Hello,
> 
> I am facing a problem with g_angle. I want to analyse some dihedrals. 
> When calculating the autocorrelation function, g_angle crashes if I want 
> to use a Legendre polynomial for the ACF. Can I somehow handle this problem?
> 
> 
The legendre polynomial only applies to vectors, and given a dihedral
you have only a scalar value. You can apply a Legendre polynomial to
e.g. bonds, to obtain NH order parameters.

> The command lines are below together with the error message. I am using 
> version 4.0.4 of Gromacs. My indexfile contains 4 atoms.
> 
> 
> DOES WORK:
> g_angle -f run01-10.trr -oc dicorr -type dihedral -n myindexfile
> 
> 
> DOES NOT WORK:
> g_angle -f run01-10.trr -oc dicorr -type dihedral -n myindexfile -P 1 
> [or 2, 3]
> ERROR MESSAGE:
> -------------------------------------------------------
> Program g_angle, VERSION 4.0.4
> Source code file: autocorr.c, line: 607
> 
> Fatal error:
> Incompatible options bCos && bVector (autocorr.c, 608)
> -------------------------------------------------------
> 
> 
> Thanks for your help
> Dennis
> 
> 
> ------------------------------------------------------------------------
> 
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-- 
David van der Spoel, Ph.D., Professor of Biology
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205. Fax: +4618511755.
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se