From: John Stone (
Date: Wed Feb 23 2011 - 13:02:12 CST

  If you want to compute only one frame, you must specify which frame
to compute. If you want the result for a single frame (the current frame
for the selection), then the "measure center" command is what you want.
The "measure avpos" command operates over all loaded frames by default,
unless you specify a particular sub-range of the trajectory frames.

  John Stone

On Thu, Feb 24, 2011 at 12:57:00AM -0600, wrote:
> Hi All,
> I have a question about command measure avpos. I want to calculate the average position of the P atoms of my lipid bilayer, and to see the change of the thickness of the lipid bilayer during the MD simulation. I loaded my dcd file, and use measure avpos [atomselect 0 "name P and Z gt 0"] to calculate the average positon of P atom of upper leaflet, but it looks like that I got all the average position for all the P atoms over the entire trajectory, could anyone please tell me what's wrong with my command?
> Thanks a lot!
> Emilia
> ___________________________________
> DICP WebMail,

NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
Email:                 Phone: 217-244-3349
  WWW:      Fax: 217-244-6078