code: public static Vec compose(TransfVec origVec, int[][] transfMap, String[] domain, boolean keepOrig) {
      // Do a mapping from INT -> ENUM -> this vector ENUM
      int[][] domMap = Utils.compose(new int[][] {origVec._values, origVec._indexes }, transfMap);
      Vec result = origVec.masterVec().makeTransf(domMap[0], domMap[1], domain);;
      if (!keepOrig) DKV.remove(origVec._key);
      return result;
    }
docs: Compose given origVector with given transformation. Always returns a new vector.
  Original vector is kept if keepOrig is true.
  @param origVec
  @param transfMap
  @param keepOrig
  @return a new instance of {@link TransfVec} composing transformation of origVector and tranfsMap