From: Monika Madhavi (
Date: Fri Mar 06 2015 - 02:56:46 CST

Dear all

I want to select all the atoms in my simulation box and select some N
number of atoms from it. I want to select the atoms from my trajectory,
mytraj.dcd file. I wrote a tcl script "trace.tcl" which contains a
procedure called "trace" which takes N as the argument.

This is the structure of trace.tcl

proc trace {N} {

set sel [atomselect top all]
set dim [measure minmax $sel]
some more steps..............

in vmd I loaded my .dcd file and .psf file and then in Tkconsole I typed
source trace.tcl
trace 10

this gives me an error "measure minmax: no atom selection"

I cannot understand why I get this error and how to stop that. I am very
grateful to anyone who can help.

Thank you.

W.A.Monika Madhavi
Lecturer (Probation),
Department of Physics,
University of Colombo.