basis3d {gellipsoid}

Draw Basis Vectors in an rgl Scene

Description

The function calculates and optionally draws basis vectors to be used as coordinate axes in an rgl 3D display. For geometric diagrams and some data displays, this can be more useful than using axis3d or box3d to provide guides or axes. The origin argument permits multiple diagrams or graphs in the same display, each with their own coordinate axes.

Usage

basis3d(
  matrix = diag(3),
  origin = c(0, 0, 0),
  scale = 1,
  draw = TRUE,
  label = draw,
  texts = colnames(basis),
  lwd = 3,
  cex = 2,
  ...
)

Arguments

matrix

A 3 x 3 matrix, whose columns are the basis vectors, typically of unit length.

origin

Origin in the rgl scene of the basis vectors

scale

Scaling factor for the basis vectors

draw

If TRUE, the vectors are plotted

label

If TRUE, the vectors are labeled at their tips

texts

A character vector of length 3 used for labels. Defaults to c("x", "y", "z").

lwd

Line width for vectors

cex

Character size for labels

...

Other arguments, passed to segments3d and text3d

Value

Returns invisibly a 6 x 3 matrix, whose columns are the coordinate axes, c("x", "y", "z"). Odd numbered rows give the coordinates of the origin, while even numbered rows give the locations of the tips of the vectors.

Author(s)

Michael Friendly

See Also

axis3d, box3d

Examples

# show two different sets of basis vectors
open3d()
basis3d()
A <- matrix(c(1,2,0.1,
              2,1,0.1,
              0.1,0.1,0.5), 3,3)
basis3d(t(A), col="red")

# scene with two different displays
open3d()
basis3d()
basis3d(origin=c(2,0,0))