Scale vectors to fill the current plot

Calculates a scale factor so that a collection of vectors nearly fills the current plot, that is, the longest vector does not extend beyond the plot region.

Usage

vecscale(
  vectors,
  bbox = matrix(par("usr"), 2, 2),
  origin = c(0, 0),
  factor = 0.95
)

Arguments

vectors: a two-column matrix giving the end points of a collection of vectors
bbox: the bounding box of the containing plot region within which the vectors are to be plotted. The default is the bounding box of the current plot window, obtained from par("usr").
origin: origin of the vectors. Defaults to (0, 0).
factor: maximum length of the rescaled vectors relative to the maximum possible

Value

scale factor, the numeric multiplier of the vectors

Details

This function is used in, e.g., vectors() to draw labeled vectors in a dimension-reduction plot. The scaling calculated here doesn't directly calculate space for the labels to fit within the plot regions. The factor argument can provide for that, shrinking the vectors by that factor.

Author

Michael Friendly

Examples


bbox <- matrix(c(-3, 3, -2, 2), 2, 2)
colnames(bbox) <- c("x","y")
rownames(bbox) <- c("min", "max")
bbox
#>      x  y
#> min -3 -2
#> max  3  2

vecs <- matrix( runif(10, -1, 1), 5, 2)

plot(bbox)
arrows(0, 0, vecs[,1], vecs[,2], angle=10, col="red")
(s <- vecscale(vecs))
#> [1] 3.106133
arrows(0, 0, s*vecs[,1], s*vecs[,2], angle=10)