x: DISTANCE ATOMS=1,2
w: READ FILE=weights.dat VALUES=w IGNORE_TIME 

HISTOGRAM ...
  ARG=x
  GRID_MIN=0.0
  GRID_MAX=3.0
  GRID_BIN=100
  LOGWEIGHTS=w
  BANDWIDTH=0.5
  LABEL=hA1
... HISTOGRAM

DUMPGRID GRID=hA1 FILE=histoA1 STRIDE=1 FMT=%8.4f
