# arrows3d: Draw 3D arrows In matlib: Matrix Functions for Teaching and Learning Linear Algebra and Multivariate Statistics

## Description

Draws nice 3D arrows with `cone3d`s at their tips.

## Usage

 ```1 2``` ```arrows3d(coords, headlength = 0.035, head = "end", scale = NULL, radius = NULL, ref.length = NULL, draw = TRUE, ...) ```

## Arguments

 `coords` A 2n x 3 matrix giving the start and end (x,y,z) coordinates of n arrows, in pairs. The first vector in each pair is taken as the starting coordinates of the arrow, the second as the end coordinates. `headlength` Length of the arrow heads, in device units `head` Position of the arrow head. Only `head="end"` is presently implemented. `scale` Scale factor for base and tip of arrow head, a vector of length 3, giving relative scale factors for X, Y, Z `radius` radius of the base of the arrow head `ref.length` length of vector to be used to scale all of the arrow heads (permits drawing arrow heads of the same size as in a previous call); if `NULL`, arrows are scaled relative to the longest vector `draw` if `TRUE` (the default) draw the arrow(s) `...` rgl arguments passed down to `segments3d` and `cone3d`, for example, `col` and `lwd`

## Details

This function is meant to be analogous to `arrows`, but for 3D plots using `rgl`. `headlength`, `scale` and `radius` set the length, scale factor and base radius of the arrow head, a 3D cone. The units of these are all in terms of the ranges of the current rgl 3D scene.

## Value

invisibly returns the length of the vector used to scale the arrow heads

## Author(s)

January Weiner, borrowed from the pca3d package, slightly modified by John Fox

`vectors3d`
Other vector diagrams: `Proj`, `arc`, `corner`, `plot.regvec3d`, `pointOnLine`, `regvec3d`, `vectors3d`, `vectors`
 `1` ``` #none yet ```