angle2d: Determine angle
In gear: Geostatistical Analysis in R

Description Usage Arguments Details Value Author(s) Examples

angle2d determines the angle between pairs of coordinates in degrees or radians. The coordinates are assumed to be in two-dimensional space.

1	angle2d(coords1, coords2, radians = FALSE, invert = TRUE)

`coords1`	An N \times 2 matrix of spatial coordinates.
`coords2`	An N \times 2 matrix of spatial coordinates.
`radians`	A logical value indicating whether the angles returned should be in degrees or radians. The default is `FALSE`, indicating that the returned angles are in degrees.
`invert`	A logical value indicating whether the axes of the coordinates should be inverted (i.e., the x- and y-axis are switched). The default is `TRUE` to mimic results from other geostatistical R packages like `gstat`, `geoR`, and other software like `GSLIB` and `GeoEAS`. Set to `FALSE` to use the typical x- and y-axes.

Note that the angle is between the actual pairs of points, not the angle between the vectors extending from the origin to the points. e.g., the angle between (0, 1) and (1, 1) is 90 degrees, not 45. The sign of the direction not accounted for, e.g., a -135 degree angle is rotated by 180 degrees to become a 45 degree angle. All angles returned are in the interval [0, 180].

Returns a vector of angles.

Joshua French

coords1 = matrix(0, nrow = 8, ncol = 2)
coords2 = cbind(c(2, 2, 0, -2, -2, -2, 0, 2), c(0, 2, 2, 2, 0, -2, -2, -2))
angle2d(coords1, coords2)
angle2d(coords1, coords2, radians = TRUE)