[gmx-users] Trjconv: reducing frames and Time issue

[Alan Dodd]

Don't use -timestep.  Just -skip will do for what you want.

----- Original Message ----
From: "bmmothan at ucalgary.ca" <bmmothan at ucalgary.ca>
To: gmx-users at gromacs.org
Sent: Tuesday, May 8, 2007 7:20:39 PM
Subject: [gmx-users] Trjconv: reducing frames and Time issue


Hello All,

I have a xtc file and I used trjconv on it to reduce the number of frames 
using:

trjconv -f original.xtc -o reduced-frames.xtc -s xx.tpr  -timestep 20 -fit
rot+trans -skip 2 -center no

Now I have two  xtc files for a 10ns simulation:
original.xtc
reduced-frames.xtc

I did gmxcheck to check the number of frames and time (I will show  the
results for both below). The problem is: the number of frames is reduced
by half however the time shown on the reducedframes.xtc is increased!!
(from 10 000 ps to 100 000 ps).. I cant understand what this means? I did
a g-cluster analysis and they r saying I did a 100 000ps simulation which
it not true! can anyone explain this to me?

original.xtc

Reading frame       0 time    0.000
# Atoms  5100
Precision 0.001 (nm)
Last frame       5000 time 10000.000


Item        #frames Timestep (ps)
Step          5001    2
Time          5001    2
Lambda           0
Coords        5001    2
Velocities       0
Forces           0
Box           5001    2

reduced-frames.xtc
Reading frame       0 time    0.000
# Atoms  92
Precision 0.001 (nm)
Last frame       2500 time 100000.000


Item        #frames Timestep (ps)
Step          2501    40
Time          2501    40
Lambda           0
Coords        2501    40
Velocities       0
Forces           0
Box           2501    40


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