First-date of invasion

Estimate a surface of first-date of invasion, given a sparse set of observation locations and times.

sr_fdoi(x, estimation_mask)

Arguments

x	A sr_obs object defined with sr_obs.
estimation_mask	A raster template for results.

Value

A RasterLayer with estimated dates of invasion at each pixel.

Details

This function first takes the earliest observed case in a neighbourhood, as defined by the parameter neigh_tol in the definition of x. Next, it interpolates the earliest observations with a smooth surface, using a Thin-Plate splines model.

Examples

d <- data.frame(lon = runif(30), lat = runif(30))
d <- transform(d, date = round(10 * sqrt(lon**2 + lat**2)))
sro <- sr_obs(d, "date")
r <- raster(st_sf(sro), vals = 1)
fdoi <- sr_fdoi(sro, r)
plot(fdoi, col = hcl.colors(12))
points(d)