# How does one use the qhull optional package?

Has anyone used the qhull optional package? I'm not so sure on how to use it. Is there a tutorial on this?

How does one use the qhull optional package?

1

First, you can install it by typing:

```
$ sage -i qhull
```

Then, i do not think that there in an interface with `qhull`

inside Sage. So, you have to use it from a shell, as if you installed it on your OS:

```
$ sage -sh
```

To get help and examples, just type:

```
(sage-sh) user@machine:~$ qhull
```

And then, you can try one of the examples:

```
(sage-sh) user@machine:~$ rbox y 1000 W0 | qhull
Convex hull of 1004 points in 3-d:
Number of vertices: 4
Number of facets: 4
Statistics for: rbox y 1000 W0 | qhull
Number of points processed: 4
Number of hyperplanes created: 5
Number of distance tests for qhull: 11001
CPU seconds to compute hull (after input): 0
```

To get informations about `rbox`

, just type:

```
(sage-sh) user@machine:~$ rbox
```

**EDIT** : `qhull`

is shipped with `scipy`

(and also with `matplotlib`

from version 1.4), so you could benefit from their Cython interface to use `qhull`

features within Sage (Delaunay triangulation, Voronoi tesselation, convex hull), see this page.

0

I'll expand on tmonteil's last comment: there is an interface to qhull included on scipy!

For example, this code computes the hull of a random set of **2D** points:

```
import numpy as np
from scipy.spatial import ConvexHull
points = np.random.rand(30, 2) # 30 random points in 2-D
hull = ConvexHull(points)
```

and this code plots it:

```
my_plot = point2d(points)
for simplex in hull.simplices:
my_plot += line2d([points[v,:] for v in simplex])
my_plot
```

While this code computes the hull of a random set of **3D** points:

```
import numpy as np
from scipy.spatial import ConvexHull
points = np.random.rand(30, 3) # 30 random points in 3-D
hull = ConvexHull(points)
```

and this code plots it:

```
my_plot = point3d(points)
for simplex in hull.simplices:
my_plot += line3d([points[simplex[-1],:]]+[points[v,:] for v in simplex])
my_plot
```

Asked: **
2013-06-18 14:22:00 -0500
**

Seen: **531 times**

Last updated: **Jan 26 '17**

How to draw figures of Polygons in SageMath

Number of line segments in a group - algorithm

Sage: christoffel symbol calculation issue, help...

Computing the volume of a polytope that is not full-dimensional

How can I sketch the graph in sagemath like picture?

how to connect 2D polygons and show in 3D?

Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.

Sorry. Deleted my post. I misread your question about installing, whereas you asked about *using*.