R/intersectPolyCircle.R

In surveillance: Temporal and Spatio-Temporal Modeling and Monitoring of Epidemic Phenomena

################################################################################
### Compute the intersection of a circular domain with a polygonal domain of
### various classes (currently: "owin" or "SpatialPolygons")
###
### Copyright (C) 2009-2015 Sebastian Meyer
###
### This file is part of the R package "surveillance",
### free software under the terms of the GNU General Public License, version 2,
### a copy of which is available at https://www.R-project.org/Licenses/.
################################################################################


intersectPolyCircle.owin <- function (object, center, radius, npoly = 32, ...)
{
    circle <- disc(radius = radius, centre = center, npoly = npoly)
    res <- intersect.owin(circle, object)  # order does not affect runtime
    ## ensure "polygonal" type (because of rescue.rectangle in intersect.owin)
    as.polygonal(res)
}

intersectPolyCircle.SpatialPolygons <- function (object, center, radius,
                                                 npoly = 32, ...)
{
    .Defunct()
    ## FIXME: could implement and wrap a method for sf polygons
    ##intersectPolyCircle.sfc(sf::st_as_sfc(object), center, radius, npoly, ...)
}

## intersectPolyCircle.sfc <- function (object, center, radius, npoly = 32, ...)
## {
##     ## FIXME: assert polygonal object
##     circle <- discpoly(center, radius, npoly = npoly, class = "sfg") # or sfc?
##     sf::st_intersection(object, circle)
## }