group {<xray-average-group-statement>} end

<xray-average-group-statement> :==

  [mask=<real-space-object>]
  --{The real space object containing an averaging mask. This mask covers
     the primary molecule (group 1). If this mask is not defined for a group
     then it will be generated from the mask of the primary group (group 1).
     This decreases the amount of memory required at the cost of increased
     computing time.}
  <matrix>
  --{The rotation matrix for this group.}
  translation=<vector>
  --{The translation vector for this group.}