cdm/src/main/java/ucar/nc2/Structure.java
public Structure select( List<String> memberNames) {
    Structure result = (Structure) copy();
    List<Variable> members = new ArrayList<>();
    for (String name : memberNames) {
      Variable m = findVariable(name);
      if (null != m) members.add(m);
    }
    result.setMemberVariables(members);
    result.isSubset = true;
    return result;
  }
public Structure select( List<String> memberNames) {
    Structure result = (Structure) copy();
    List<Variable> members = new ArrayList<>();
    for (String name : memberNames) {
      Variable m = findVariable(name);
      if (null != m) members.add(m);
    }
    result.setMemberVariables(members);
    result.isSubset = true;
    return result;
  }
Create a subset of the Structure consisting only of the given member variables
@param memberNames list of Variable names, already a member
@return Structure containing just those members