[gmx-users] gmx distance

[antonia vyrkou]

Hello,

I am trying to calculate the average distance between the centers of mass
of two groups using the tool
gmx distance

The index file I am using is the following
[ ASN137 ]
1056 3625 6194 8763
[ PYRO3 ]
20558 20612 20666 20720

And I specify
 com of group "PYRO3" and within 0.4 of com of group "ASN137"

When I press enter it types
Selection 'com of group "PYRO3" and within 0.4 of com of group "ASN137"'
parsed

I then get the error message
Selection 'com of group "PYRO3" and within 0.4 of com of group "ASN137"'
does
not evaluate into an even number of positions (there are 1 positions)

I found a similar problem at the mail archives and the answer was ">* In
other words, the selections resemble those that were earlier required by*

>* g_bond, not those by g_dist. The wiki page on tool changes for 5.0 shows an
*>* example if using "plus" in a selection to get the behavior of g_dist to
*>* compute the distance between centers-of-mass of two groups."*

The problem is that I cannot find the example mentioned. Could you
please help me with that?

Thank you

Antonia