sample.annulus: Sample annulus

In jeffreyevans/spatialEco: Spatial Analysis and Modelling Utilities

Sample annulus

Description

Creates sample points based on annulus with defined inner and outer radius

Usage

sample.annulus(x, r1, r2, size = 10, ...)

Arguments

x	An sf POINT class object
r1	Numeric value defining inner radius of annulus (in projection units)
r2	Numeric value defining outer radius of annulus (in projection units)
size	Number of samples
...	Additional arguments passed to sf::st_sample

Details

Function can be used for distance based sampling which is a sampling method that can be used to capture spatially lagged variation.

Value

sf POINTS object

Author(s)

Jeffrey S. Evans <[e-mail]>

Examples

 library(sf)
 if(require(sp, quietly = TRUE)) {
   data(meuse, package = "sp")
   meuse <- st_as_sf(meuse, coords = c("x", "y"), crs = 28992, 
                     agr = "constant")

 xy <- meuse[2,]
 rs100 <- sample.annulus(xy, r1=50, r2=100, size = 50)
 rs200 <- sample.annulus(xy, r1=100, r2=200, size = 50)
 
 plot(st_geometry(rs200), pch=20, col="red")
   plot(st_geometry(rs100), pch=20, col="blue", add=TRUE)
   plot(st_geometry(xy), pch=20, cex=2, col="black", add=TRUE)
 legend("topright", legend=c("50-100m", "100-200m", "source"), 
        pch=c(20,20,20), col=c("blue","red","black"))


# Run on multiple points
rs100 <- sample.annulus(meuse[1:3,], r1=50, r2=100, 
                        size = 50)
rs200 <- sample.annulus(meuse[1:3,], r1=50, r2=200, 
                        size = 50)
plot(st_geometry(rs200), pch=20, col="red")
  plot(st_geometry(rs100), pch=20, col="blue", add=TRUE)
    plot(st_geometry(meuse[1:3,]), pch=20, cex=2, col="black", add=TRUE)
 legend("topright", legend=c("50-100m", "100-200m", "source"), 
        pch=c(20,20,20), col=c("blue","red","black"))

} else { 
  cat("Please install sp package to run example", "\n")
}

jeffreyevans/spatialEco documentation built on April 4, 2024, 10:53 a.m.