function a = r83v_to_r8vec ( m, n, a1, a2, a3 )

%*****************************************************************************80
%
%% R83V_TO_R8VEC copies an R83V matrix to an R8VEC.
%
%  Discussion:
%
%    The R83V storage format is used for a tridiagonal matrix.
%    The subdiagonal is in A(min(M-1,N)).
%    The diagonal is in B(min(M,N)).
%    The superdiagonal is in C(min(M,N-1)).
%
%  Example:
%
%    An R83V matrix of order 3x5 would be stored:
%
%      B1  C1  **  **  **
%      A1  B2  C2  **  **
%      **  A2  B3  C3  **
%
%    An R83 matrix of order 5x5 would be stored:
%
%      B1  C1  **  **  **
%      A1  B2  C2  **  **
%      **  A2  B3  C3  **
%      **  **  A3  B4  C4
%      **  **  **  A4  B5
%
%    An R83 matrix of order 5x3 would be stored:
%
%      B1  C1  **
%      A1  B2  C2
%      **  A2  B3
%      **  **  A3
%      **  **  **
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    20 February 2016
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer M, N, the order of the matrix.
%
%    Input, real A1(min(M-1,N)), A2(min(M,N)), A3(min(M,N-1)), the matrix.
%
%    Output, real R83V_TO_R8VEC(min(M-1,N)+min(M,N)+min(M,N-1)), the vector.
%
  k = 0;
  for j = 1 : n
    if ( j <= m + 1 && 2 <= j )
      k = k + 1;
      a(k) = a3(j-1);
    end
    if ( j <= m )
      k = k + 1;
      a(k) = a2(j);
    end
    if ( j <= m - 1 )
      k = k + 1;
      a(k) = a1(j);
    end
  end

  return
end
