code: @Override
      public DMatrixRMaj getT(DMatrixRMaj T ) {
          T = UtilDecompositons_DDRM.checkZeros(T,N,N);
  
          T.data[0] = QT.data[0];
  
          for( int i = 1; i < N; i++ ) {
              T.set(i,i, QT.get(i,i));
              double a = QT.get(i-1,i);
              T.set(i-1,i,a);
              T.set(i,i-1,a);
          }
  
          if( N > 1 ) {
              T.data[(N-1)*N+N-1] = QT.data[(N-1)*N+N-1];
              T.data[(N-1)*N+N-2] = QT.data[(N-2)*N+N-1];
          }
              
          return T;
      }
docs: Extracts the tridiagonal matrix found in the decomposition.
  
  @param T If not null then the results will be stored here.  Otherwise a new matrix will be created.
  @return The extracted T matrix.