shotGroups (version 0.2-2)

getMinBBox: Minimum-area bounding box for a set of 2D-points

Description

Calculates the vertices of the minimum-area, possibly oriented bounding box given a set of 2D-coordinates.

Usage

getMinBBox(xy)

Arguments

xy

a numerical (n x 2)-matrix with the (x,y)-coordinates of n >= 2 points (1 row of coordinates per point).

Value

• A list with the following information about the minimum-area bounding box:
• pts
  a (4 x 2)-matrix containing the coordinates of the (ordered) vertices.
• width
  width of the box.
• height
  height of the box.
• angle
  orientation of the box' longer edge pointing up as returned by atan2, but in degree.

See Also

drawBox2, getBoundingBox, getMinCircle

Examples

xy <- matrix(round(rnorm(16, 100, 15)), ncol=2)
bb <- getMinBBox(xy)                     # minimum bounding box
H  <- chull(xy)                          # convex hull

# plot original points, convex hull, and minimum bounding box
plot(xy, xlim=range(c(xy[ , 1], bb$pts[ , 1])),
         ylim=range(c(xy[ , 2], bb$pts[ , 2])), asp=1, pch=16)
polygon(xy[H, ], col=NA)                 # show convex hull
drawBox2(bb$pts, fg='blue', colCtr='blue', pch=4, cex=2)

bb$width * bb$height                     # box area
bb$angle                                 # box orientation