Extract entities of the supplied type(s).
id = extract(grp,type)
id = grp.extract([grp.type.gNode grp.type.gElement])
EXTRACT extracts the entities of the specified types from the scalar IMAT_GROUP GRP. TYPE is a numeric vector corresponding to the types defined by IMAT_GROUP.TYPE.
>> id = extract(grp,imat_group.type.gNode)