// submatrix types:
  //
  // .submat(first_row, first_column, last_row, last_column)
  // .row(row_number)
  // .col(column_number)
  // .cols(first_column, last_column)
  // .rows(first_row, last_row)

  cout << "C.submat(0,0,3,1) =" << endl;
  cout << C.submat(0,0,3,1) << endl;

  // generate the identity matrix
  mat D = eye<mat>(4,4);

  D.submat(0,0,3,1) = C.cols(1,2);
  D.print("D:");

  // transpose
  cout << "trans(B) =" << endl;
  cout << trans(B) << endl;

  // maximum from each column (traverse along rows)
  cout << "max(B) =" << endl;
  cout << max(B) << endl;