Error in the collective variables

From: Jiali Wang (jwang204_at_binghamton.edu)
Date: Tue Nov 19 2019 - 12:48:25 CST

Dear NAMD users,
Good afternoon,I have trouble in collective variable, when i am collecting
Z positions in Colvars. I found the distance collected is from main
atomnumbers to ref atomnumbers. But what I want to collect is absolute Z
positions (like reference atom is (0,0,0)), Do you know how to set this? I
try to use dummyatom as reference atom, it can't recognize it. and if I
make anychange, does it affect harmonic constant part?
Thank you for your time.
Jiali

here is my colvars file.
colvar {
   name length
   lowerboundary -19.0
   upperboundary 10.0

   lowerwallconstant 100.0
   upperwallconstant 100.0

  outputAppliedForce off
  distanceZ {
    main {
      atomNumbers 19021}
ref {
 refPositions (0.0, 0.0, 0.0)}
 axis ( 0.0, 0.0, 1.0 )
    }
  }
harmonic {
  name lenZ
  colvars length
  forceConstant 1 # in kcal/mol/A^2

  centers -1.0 # go from 25 Angstrom RMSD...

  outputCenters on

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