MATLAB Function Reference |

**Syntax**

**Description**

```
K = convhull(x,y)
```

returns indices into the `x`

and `y`

vectors of the points on the convex hull.

```
[K,a] = convhull(x,y)
```

also returns the area of the convex hull.

**Visualization**

Use `plot`

to plot the output of `convhull`

.

**Examples**

xx = -1:.05:1; yy = abs(sqrt(xx)); [x,y] = pol2cart(xx,yy); k = convhull(x,y); plot(x(k),y(k),'r-',x,y,'b+')

**Algorithm**

`convhull`

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 **

`convhulln`

, `delaunay`

, `plot`

, `polyarea`

, `voronoi`

**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.

conv2 | convhulln |