incidmat              package:mathgraph              R Documentation

_I_n_c_i_d_e_n_c_e _M_a_t_r_i_x _f_o_r _a _M_a_t_h_e_m_a_t_i_c_a_l _G_r_a_p_h

_D_e_s_c_r_i_p_t_i_o_n:

     Returns an object of class '"incidmat"' which is a matrix
     indicating the start and end node for each edge in the graph.

_U_s_a_g_e:

     incidmat(x, ...)
     incidmat.mathgraph(x, expand=TRUE, general=FALSE, ...)

     is.incidmat(x)

_A_r_g_u_m_e_n_t_s:

       x: object representing a mathematical graph. 

  expand: logical flag: if 'TRUE', then undirected edges are 
          represented by two columns in the output.
           If 'FALSE', then both non-zero elements of an undirected
          edge  are positive. 

 general: logical flag: if 'TRUE', then there is a non-zero  entry in a
          column representing a loop. 

     ...: generic arguments. 

_D_e_t_a_i_l_s:

     The 'incidmat' function is generic, with a method for  class
     '"mathgraph"'.

     'is.incidmat' is the membership function for this class.

_V_a_l_u_e:

     an object of class '"incidmat"' which is a matrix with rows
     representing nodes and columns representing edges.
      Generally speaking, there is a '1' in the location where an edge
     begins and a '-1' in the location where it ends.
      Frank Harary defines incidence matrix with expand = 'FALSE'.

_N_o_t_e:

     From S Poetry, Patrick J. Burns, Section 13.3, p. 312  <URL:
     http://www.burns-stat.com/pages/spoetry.html>

_A_u_t_h_o_r(_s):

     Nick Efthymiou

_R_e_f_e_r_e_n_c_e_s:

     Chachra, V., Ghare, P. M. and Moore, J. M. (1979).  Applications
     of Graph Theory Algorithms. Elvesier North Holland, New York.

     Harary, Frank (1969). Graph Theory, p. 160. Addison Wesley.

_S_e_e _A_l_s_o:

     'adjamat', 'mathgraph', 'getpath.incidmat'

_E_x_a_m_p_l_e_s:

     incidmat(mathgraph(~ 1:3 / 3:5, dir=TRUE))
     incidmat(mathgraph(~ 1:3 / 3:5, dir=FALSE))
     incidmat(mathgraph(~ 1:3 / 3:5, dir=FALSE), expand=FALSE)

