An R package that provides a function (make_focal_matrix) to create matrices
of circular or sector neighbourhoods for use with the focal function in the
terra package. It also includes a few utility functions to work with compass
bearings such as converting bearings to and from Cartesian angles and determining
the direction and angle of the shortest rotation between two bearings.
install.packages("remotes") # if you don't already have it
remotes::install_github("mbedward/focalutils")Create a circular focal matrix of radius 50 cells, where neighbourhood cells
have a value of 1 and outside cells have NA:
library(focalutils)
m <- make_focal_matrix(50)
plot_focal_matrix(m)Create the same neighbourhood but exclude the centre cell:
m <- make_focal_matrix(50, include_centre = FALSE)
plot_focal_matrix(m)Create a sector neighbourhood spanning 90 degrees and facing west:
m <- make_focal_matrix(50, start_bearing = 225, end_bearing = 315)
plot_focal_matrix(m)Create the complement of the last neighbourhood: a circular neighbourhood that excludes the 90 degree sector facing west (Pacman!)
m <- make_focal_matrix(50, start_bearing = 315, end_bearing = 225)
plot_focal_matrix(m)