##### Extract a list of triangles from a triangulation object

This function extracts a list of triangles
from an triangulation object created by `tri.mesh`

.

- Keywords
- spatial

##### Usage

`triangles(tri.obj)`

##### Arguments

- tri.obj
object of class

`triSht`

##### Details

The vertices in the returned matrix (let's denote it with
`retval`

) are ordered counterclockwise. The columns `tr`

\(x\)
and `arc`

\(x\), \(x=1,2,3\) index the triangle and arc, respectively,
which are opposite (not shared by) node `node`

\(x\), with
`tri`

\(x=0\) if `arc`

\(x\) indexes a boundary arc. Vertex indexes
range from 1 to \(n\), the number of nodes, triangle indexes from 0
to \(nt\), and arc indexes from 1 to \(na = nt+n-1\).

##### Value

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.

##### See Also

`triSht`

, `print.triSht`

,
`plot.triSht`

, `summary.triSht`

,
`triangles`

##### Examples

```
# NOT RUN {
# use the smallest Franke data set
data(franke)
fr3.tr<-tri.mesh(franke$ds3$x, franke$ds3$y)
triangles(fr3.tr)
# }
```

*Documentation reproduced from package interp, version 1.0-33, License: GPL (>= 2)*