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Sample from a circle using the Uniform distribution

Source: R/sample_from_uniform_circle.R
sample_from_uniform_circle.Rd

This function samples a new observations point of a species within the uncertainty circle around each observation assuming a Uniform distribution.

Usage

sample_from_uniform_circle(observations, seed = NA)

Arguments

observations

An sf object with POINT geometry and a time_point and coordinateUncertaintyInMeters column. If the former column is not present, the function will assume a single time point. If the latter column is not present, the function will assume no uncertainty (zero meters) around the observation points.

seed

A positive numeric value setting the seed for random number generation to ensure reproducibility. If NA (default), then set.seed() is not called at all. If not NA, then the random number generator state is reset (to the state before calling this function) upon exiting this function.

Value

An sf object with POINT geometry containing the locations of the sampled occurrences and a coordinateUncertaintyInMeters column containing the coordinate uncertainty for each observation.

See also

Other designation: sample_from_binormal_circle()

Examples

library(sf)

# Create four random points
n_points <- 4
xlim <- c(3841000, 3842000)
ylim <- c(3110000, 3112000)
coordinate_uncertainty <- rgamma(n_points, shape = 5, rate = 0.1)

observations_sf <- data.frame(
  lat = runif(n_points, ylim[1], ylim[2]),
  long = runif(n_points, xlim[1], xlim[2]),
  time_point = 1,
  coordinateUncertaintyInMeters = coordinate_uncertainty
) %>%
  st_as_sf(coords = c("long", "lat"), crs = 3035)

# Sample points within uncertainty circles according to uniform rules
sample_from_uniform_circle(
  observations = observations_sf,
  seed = 123
)
#> Simple feature collection with 4 features and 2 fields
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 3841383 ymin: 3110074 xmax: 3841859 ymax: 3111938
#> Projected CRS: ETRS89-extended / LAEA Europe
#>   time_point coordinateUncertaintyInMeters                geometry
#> 1          1                     24.988479 POINT (3841383 3110460)
#> 2          1                    111.470650 POINT (3841446 3111938)
#> 3          1                      7.296073 POINT (3841606 3110807)
#> 4          1                     37.690618 POINT (3841859 3110074)