r1:   RMSD REFERENCE=ref1.pdb  TYPE=OPTIMAL-FAST NUMERICAL_DERIVATIVES NOPBC
r2:   RMSD REFERENCE=ref1.pdb  TYPE=OPTIMAL-FAST NUMERICAL_DERIVATIVES NOPBC
r3:   RMSD REFERENCE=ref1.pdb  TYPE=OPTIMAL-FAST NUMERICAL_DERIVATIVES NOPBC
r4:   RMSD REFERENCE=ref1.pdb  TYPE=OPTIMAL-FAST NUMERICAL_DERIVATIVES NOPBC
r5:   RMSD REFERENCE=ref1.pdb  TYPE=OPTIMAL-FAST NUMERICAL_DERIVATIVES NOPBC

PRINT ...
  STRIDE=1
  ARG=*
  FILE=COLVAR FMT=%6.3f
... PRINT

ENDPLUMED

