Calculate isotropic Sum of Exponentially Decaying Contributions (SEDC) covariates

Usage

sum_edc(
  from = NULL,
  locs = NULL,
  locs_id = NULL,
  decay_range = NULL,
  target_fields = NULL,
  C0 = NULL,
  use_threshold = TRUE,
  geom = FALSE
)

Arguments

from: SpatVector(1). Point locations which contain point-source covariate data.
locs: sf/SpatVector(1). Locations where the sum of exponentially decaying contributions are calculated.
locs_id: character(1). Name of the unique id field in point_to.
decay_range: numeric(1). Distance at which the source concentration is reduced to exp(-3) (approximately -95 %)
target_fields: character(varying). Field names in characters.
C0: NULL, character(1), or numeric vector of length nrow(from). Optional initial source values at pollutant locations. If NULL (default), all source values are set to 1. If character(1), the value is treated as a column name in from and used as source values.
use_threshold: logical(1). If TRUE (default), include only source points within 5 * decay_range from each target location. If FALSE, include all source points in from.
geom: FALSE/"sf"/"terra".. Should the function return with geometry? Default is FALSE, options with geometry are "sf" or "terra". The coordinate reference system of the sf or SpatVector is that of from.

Value

a data.frame (tibble) or SpatVector object with input field names with a suffix "_sedc" where the sums of EDC are stored. Additional attributes are attached for the EDC information.

`attr(result, "decay_range")“: the range where concentration reduces to approximately five percent
`attr(result, "sedc_threshold")“: the threshold distance at which emission source points are excluded beyond that

Note

The function is originally from chopin Distance calculation is done with terra functions internally. Thus, the function internally converts sf objects in point_* arguments to terra. The threshold should be carefully chosen by users.

References

Messier KP, Akita Y, Serre ML (2012). “Integrating Address Geocoding, Land Use Regression, and Spatiotemporal Geostatistical Estimation for Groundwater Tetrachloroethylene.” Environmental Science & Technology, 46(5), 2772–2780. ISSN 0013-936X. doi:10.1021/es203152a .

Wiesner C (????). “Euclidean Sum of Exponentially Decaying Contributions Tutorial.”

Author

Insang Song

Examples

## NOTE: Example is wrapped in `\dontrun{}` as function requires a large
##       amount of data which is not included in the package.
if (FALSE) { # \dontrun{
set.seed(101)
ncpath <- system.file("gpkg/nc.gpkg", package = "sf")
nc <- terra::vect(ncpath)
nc <- terra::project(nc, "EPSG:5070")
pnt_locs <- terra::centroids(nc, inside = TRUE)
pnt_locs <- pnt_locs[, "NAME"]
pnt_from <- terra::spatSample(nc, 10L)
pnt_from$pid <- seq(1, 10)
pnt_from <- pnt_from[, "pid"]
pnt_from$val1 <- rgamma(10L, 1, 0.05)
pnt_from$val2 <- rgamma(10L, 2, 1)

vals <- c("val1", "val2")
sum_edc(pnt_locs, pnt_from, "NAME", 1e4, vals)
} # }