MATLAB Function Reference |

**Syntax**

**Description**

```
K = convhulln(X)
```

returns the indices `K`

of the points in `X`

that comprise the facets of the convex hull of `X`

. `X`

is an `m`

-by-`n`

array representing `m`

points in `n`

-D space. If the convex hull has `p`

facets then `K`

is `p`

-by-`n`

.

```
[K,v] = convhulln(X)
```

also returns the volume `v`

of the convex hull.

**Visualization**

Plotting the output of `convhulln`

depends on the value of `n`

:

- For
`n = 2`

, use`plot`

as you would for`convhull`

. - For
`n = 3`

, you can use`trisurf`

to plot the output. The calling sequence is

- For more control over the color of the facets, use
`patch`

to plot the output. For an example, see Tessellation and Interpolation of Scattered Data in Higher Dimensions in the MATLAB documentation.

**Algorithm**

`convhulln`

is based on Qhull [2]. It uses the Qhull joggle option (`'QJ'`

). For information about `qhull`

, see http://www.geom.umn.edu/software/qhull/. For copyright information, see http://www.geom.umn.edu/software/download/COPYING.html.

**See Also**

`convhull`

, `delaunayn`

, `dsearchn`

, `tsearchn`

, `voronoin`

**Reference**

[1] Barber, C. B., D.P. Dobkin, and H.T. Huhdanpaa, "The Quickhull Algorithm for
Convex Hulls," *ACM Transactions on Mathematical Software*, Vol. 22, No. 4,
Dec. 1996, p. 469-483. Available in HTML format at http://www.acm.org/
pubs/citations/journals/toms/1996-22-4/p469-barber/ and in PostScript
format at ftp://geom.umn.edu/pub/software/qhull-96.ps.

[2] National Science and Technology Research Center for Computation and Visualization of Geometric Structures (The Geometry Center), University of Minnesota. 1993.

convhull | convn |