[gmx-users] gmx order index option

[李选选]

Hi,
I have a question of “gmx order” usage. I am studying a membrane system so I need calculate the deuterium order parameter. In some older tutorials, they said the “gmx order” can be used to do the job. The recommended command is like “gmx order -s xx.tpr -f xx.xtc -n xx.ndx -d z -nd deuter.xvg”. However, the gmx complain that I did not provide a nr option. I read through the manual of “gmx order”, it seems that two index file are necessary, -n and -nr. So what is the -nr option? Is this the index file that consists of some generic group?

Thanks a lot in advance.

Xuanxuan