Re: How to modify Convex Hull program to give output as Cartesian Coordinates?

• To: mathgroup at smc.vnet.net
• Subject: [mg48788] Re: How to modify Convex Hull program to give output as Cartesian Coordinates?
• From: "Rob Pratt" <Rob.Pratt at sas.com>
• Date: Wed, 16 Jun 2004 04:55:12 -0400 (EDT)
• References: <cam6fd\$qjj\$1@smc.vnet.net>
• Reply-to: "Rob Pratt" <Rob.Pratt at sas.com>
• Sender: owner-wri-mathgroup at wolfram.com

```"Gilmar Rodr?guez Pierluissi" <gilmar.rodriguez at nwfwmd.state.fl.us> wrote in
message news:cam6fd\$qjj\$1 at smc.vnet.net...
> Greetings Mathematica Group!:
>
> I use the following example, to formulate my question:
>
> In[1]: data2D = {{4.4, 14}, {6.7, 15.25}, {6.9, 12.8}, {2.1, 11.1},
>                 {9.5, 14.9},{13.2, 11.9}, {10.3, 12.3}, {6.8, 9.5},
>                 {3.3, 7.7}, {0.6, 5.1},{5.3, 2.4},{8.45, 4.7},
>                 {11.5, 9.6},{13.8, 7.3}, {12.9, 3.1}, {11, 1.1}};
>
> In[2]: << DiscreteMath`ComputationalGeometry`
>
> In[3]: convexhull = ConvexHull[data2D]
>
> Out[3]: {14,6,5,2,1,4,10,11,16,15}
>
> My question is:
>
> Is there any way to modify the ConvexHull program to give the
> Cartesian coordinates of the points corresponding to the values
> 14,6,5,2,1,4,10,11,16,15; instead of Out[3] above?
>
> Thank you!

In[3]: convexhull = data2D[[ConvexHull[data2D]]]

Out[3]= {{13.8, 7.3}, {13.2, 11.9}, {9.5, 14.9}, {6.7, 15.25}, {4.4, 14},

>    {2.1, 11.1}, {0.6, 5.1}, {5.3, 2.4}, {11, 1.1}, {12.9, 3.1}}

Rob Pratt

```

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