Geometries located in space (all except directions and vectors), have one or
more points supporting it. Those can be extracted and modifed with vert().
For geometries with a cardinality above one there's a choice of which support
point to extract/modify or all. Geometries consisting of more than one vertex
(segments, triangles, and tetrahedrons) also have associated edges that can
be extracted (but not modified) with edge(). edge_count() provides the
number of edges in each element in the geometry vector. The length of the
output of edge(x) is sum(edge_count(x)).
Usage
vert(x, which = NULL, ...)
vert(x, which = NULL, ...) <- value
edge(x, which = NULL, ...)
edge_count(x)Arguments
- x
A vector of geometries
- which
An integer vector giving the vertex/edge to extract, or
NULLto extract all.- ...
arguments passed on to methods
- value
An
euclid_pointvector of the same dimensionality asx
Value
A euclid_point vector for vert() or a euclid_segment vector for
edge() matching the dimensionality of x
Vertex definition
For geometries that are defined exclusively by points the definition of the
output is straight forward, e.g. for triangles vert() will extract one or
all of the corners depending on the value of which. For the other
geometries the output is defined according to the below:
circles and spheres: The vertex is the center
rays: The vertex is the source
lines and planes: The vertex is an arbitrary point on the geometry
See also
Other Geometry methods:
def(),
euclid_geometry
Examples
# Get the source vertex in a segment
s <- segment(point(3, 6), point(1, -7))
vert(s, 1)
#> <2D points [1]>
#> [1] <x:3, y:6>
# And the target
vert(s, 2)
#> <2D points [1]>
#> [1] <x:1, y:-7>
# Not providing an index extracts them all
vert(s)
#> <2D points [2]>
#> [1] <x:3, y:6> <x:1, y:-7>
# Set the source of a segment
vert(s, 1) <- point(0, 0)
s
#> <2D segments [1]>
#> [1] [<x:0, y:0>, <x:1, y:-7>]
# Get a point on a line
l <- line(4, 7, -1)
vert(l)
#> <2D points [1]>
#> [1] <x:1, y:-0.429>
# Setting the vertex of a line moves it so it runs through it
point(1, 2) %is_on% l
#> [1] FALSE
vert(l) <- point(1, 2)
point(1, 2) %is_on% l
#> [1] TRUE
# Get one of the sides from a triangle
t <- triangle(point(1, 2), point(6, 3), point(3, 1))
edge(t, 2)
#> <2D segments [1]>
#> [1] [<x:6, y:3>, <x:3, y:1>]
# or all
edge(t)
#> <2D segments [3]>
#> [1] [<x:1, y:2>, <x:6, y:3>] [<x:6, y:3>, <x:3, y:1>] [<x:3, y:1>, <x:1, y:2>]