# tri

0th

Percentile

##### A triangulation object

R object that represents the triangulation of a set of 2D points, generated by tri.mesh or add.constraint.

Keywords
spatial
##### Arguments
n

Number of nodes

x

x coordinates of the triangulation nodes

y

y coordinates of the triangulation nodes

tlist

Set of nodal indexes which, along with tlptr, tlend, and tlnew, define the triangulation as a set of $$n$$ adjacency lists -- counterclockwise-ordered sequences of neighboring nodes such that the first and last neighbors of a boundary node are boundary nodes (the first neighbor of an interior node is arbitrary). In order to distinguish between interior and boundary nodes, the last neighbor of each boundary node is represented by the negative of its index.

tlptr

Set of pointers in one-to-one correspondence with the elements of tlist. tlist[tlptr[i]] indexes the node which follows tlist[i] in cyclical counterclockwise order (the first neighbor follows the last neighbor).

tlend

Set of pointers to adjacency lists. tlend[k] points to the last neighbor of node $$k$$ for $$k = 1,...,n$$. Thus, tlist[tlend[k]]<0 if and only if $$k$$ is a boundary node.

tlnew

Pointer to the first empty location in tlist and tlptr (list length plus one).

nc

number of constraints

lc

starting indices of constraints in x and y

call

call, which generated this object

##### Note

The elements tlist, tlptr, tlend and tlnew are mainly intended for internal use in the appropriate Fortran routines.

##### References

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

tri.mesh, print.tri, plot.tri, summary.tri