Add a visualization of the system using arrows

The visualization displays the movement of a uniform array of points under the function defined by the model as arrows. The base of the arrow is placed on each discretized point. The tip of the head of the arrow points in the direction of the image of that point. In order to use this visualization, a discretization parameter must be set either on the range or as a parameter.

dsarrows(scale = 0.9, col = "blue", angle = 30, type = "simple",
  length = NULL, iters = 1, head.length = 0.2, discretize = NULL,
  behind = TRUE, crop = FALSE, ...)

Arguments

scale	Changes the size of the arrow to a user-specified scale relative to the discretization parameter.
col	Colors the arrows.
angle	Specifies the angle of the head of the arrow. Passed directly into shape's Arrows function.
type	Determines type of arrow. Accepted values are identical to acceptable values of arr.type in the "shape" library.
length	A non-scaled length of arrow tail. Causes scale to be ignored.
iters	Allows user to point the head of each arrow towards the result of a specified number of iterations of the function.
head.length	Changes the size of the arrowhead. Passed directly to Arrows as arr.length. When the range is large, a smaller value produces reasonable results.
discretize	Overrides the discretization parameter defined in the range.
behind	Forces the arrows to be a background object for the purposes of layering.
crop	If crop==TRUE then arrows whose image falls outside the range are not displayed.
...	Further graphical parameters passed to Arrows

Details

The arrows are scaled according to the discretization. If the discretization is too fine (small), the arrows may seem crowded. It is suggested to try a coarser (larger) discretization size before modifying the size of the arrows.

The most common way to invoke dsarrows is to simply add model + dsarrows(), where model is a variable corresponding with the dsmodel class.

See also

dsdots

Examples

library(dsmodels)

fun <- function(X,Y) {
  list(
    X/exp(Y),
    Y/exp(X)
  )
}
model <- dsmodel(fun, title = "Blue Arrows")
range <- dsrange(x = -2:3, y = -2:3, discretize = .5)
model + range + dsarrows()

dsmodel(fun, title = "Spaced Purple Arrows") +
 dsrange(x = -2:3, y = -2:3, discretize = .5) +
 dsarrows(discretize = 1, col = "magenta")