code: @Override public double[] getRow() {
      if (_fr.numRows() != 1)
        throw new IllegalArgumentException("Trying to get a single row from a multirow frame: " + _fr.numRows() + "!=1");
  
      double res[] = new double[_fr.numCols()];
      for (int i = 0; i < _fr.numCols(); ++i)
        res[i] = _fr.vec(i).at(0);
      return res;
    }
docs: Extract row from a single-row frame.
  @return Array of row elements.