On 19/05/2014, 10:42 AM, Alexander Shenkin wrote:
Hi Folks,
I have a set of x,y,z points in 3D space that defines the outline of a
tree crown (5 - 15 perimeter points + 1 top & bottom point). I would
like to calculate the volume of the corresponding 3D polygon based on
those points. I have been able to use geometry::convhulln, but I think
this isn't the right algorithm, since the polygon needs to pass through
each point in order, and not just snap a rubber-band around the outer
points.
Any suggestions for alternative algorithms and packages would be most
welcome!
If you aren't using the convex hull, you need to specify more
information. The vertices of a polyhedron don't have a natural order,
so passing through them "in order" doesn't make sense.
One way to specify this information is to specify which triples of
vertices form triangular faces, as convhulln does.
I don't know of a package containing code to compute the volume, but a
description of the algorithm is on this page:
http://www.ecse.rpi.edu/~wrf/Research/Short_Notes/volume.html
Duncan Murdoch
Thanks,
Allie
seq x y z
1 1 -1.7310065 2.4502278 11.1
2 2 -1.9048260 -0.6096212 9.0
3 3 2.8652209 0.8891057 11.0
4 4 2.3929514 -3.4516349 11.2
5 5 -2.6436343 5.2745803 11.7
6 6 -4.3521504 4.6924180 11.7
7 7 6.1441732 -4.8051156 11.6
8 8 -6.2157823 -3.2193244 8.0
9 9 1.0024961 -2.8275434 9.0
10 10 -3.9656821 3.0452201 8.0
11 11 4.2070518 -1.5970958 11.0
12 12 -0.9461915 1.2902409 9.8
13 13 2.2792265 0.7517491 11.4
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
