triangles              package:tripack              R Documentation

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

     This function extracts a triangulation data structure from an
     triangulation object created by 'tri.mesh'.

     The vertices in the returned matrix (let's denote it  with
     'retval') are ordered counterclockwise with the first vertex taken
     to be the one with smallest index.  Thus, 'retval[i,"node2"]' and
     'retval[i,"node3"]' are larger than 'retval[i,"node3"]' and index
     adjacent neighbors of node 'retval[i,"node1"]'. The columns 'trx'
     and 'arcx', x=1,2,3 index the triangle and arc, respectively,
     which are opposite (not shared by) node 'nodex', with 'trix'= 0 if
     'arcx' indexes a boundary arc.  Vertex indexes range from 1 to N,
     triangle indexes from 0 to NT, and, if included, arc indexes from
     1 to NA = NT+N-1.  The triangles are  ordered on first (smallest)
     vertex indexes, except that the sets of constraint triangles
     (triangles contained in the closure of a constraint region) follow
     the non-constraint triangles.

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

     triangles(tri.obj)

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

 tri.obj: object of class '"tri"'

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

     A matrix with columns 'node1','node2','node3', representing the
     vertex nodal indexes, 'tr1','tr2','tr3', representing neighboring
     triangle indexes and 'arc1','arc2','arc3' reresenting arc indexes.

     Each row represents one triangle.

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

     A. Gebhardt

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

     R. J. Renka (1996). Algorithm 751: TRIPACK: a constrained
     two-dimensional {Delaunay} triangulation package. ACM Transactions
     on Mathematical Software. *22*, 1-8.

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

     'tri', 'print.tri', 'plot.tri', 'summary.tri', 'triangles'

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

     # use a slighlty modified version of data(tritest)
     data(tritest2)
     tritest2.tr<-tri.mesh(tritest2$x,tritest2$y)
     triangles(tritest2.tr)

