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#' Shift or re-center geographical coordinates for a Pacific view
#'
#' @description
#' All longitudes < 0 are added to 360, to avoid for instance parts of Alaska
#' being represented on the far left and right of a plot because they have
#' values straddling 180 degrees. In general, using a projected
#' coordinate reference system is to be preferred, but this method permits a
#' geographical coordinate reference system to be used. This is the sf
#' equivalent of \code{\link[sp:recenter-methods]{recenter}} in the sp package and
#' ST_ShiftLongitude in PostGIS.
#'
#' @param x object of class sf or sfc
#' @param ... ignored
#'
#' @export
st_shift_longitude = function(x) {
ll = st_is_longlat(x)
if (!ll | is.na(ll))
stop("'st_shift_longitude' requires non-projected geographic coordinates",
call. = FALSE)
UseMethod("st_shift_longitude")
}
#' @name st_shift_longitude
#' @export
#' @examples
#' ## sfc
#' pt1 = st_point(c(-170, 50))
#' pt2 = st_point(c(170, 50))
#' (sfc = st_sfc(pt1, pt2))
#' sfc = st_set_crs(sfc, 4326)
#' st_shift_longitude(sfc)
#'
st_shift_longitude.sfc = function(x, ...) {
xcrs = st_crs(x)
g = (x + c(360, 90)) %% c(360) - c(0, 90)
st_wrap_dateline(st_set_crs(g - c(180, 0), xcrs)) + c(180, 0)
st_set_crs(g, xcrs)
}
#' @name st_shift_longitude
#' @export
#' @examples
#' ## sf
#' d = st_as_sf(data.frame(id = 1:2, geometry = sfc))
#' st_shift_longitude(d)
st_shift_longitude.sf = function(x, ...) {
st_geometry(x) = st_shift_longitude(st_geometry(x))
return(x)
}
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