# sample.annulus

From spatialEco v1.3-2
by Jeffrey S Evans

##### Sample annulus

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

##### Usage

`sample.annulus(x, r1, r2, n = 10, ...)`

##### Arguments

- x
sp SpatialPoints or SpatialPointsDataFrame class object

- r1
Numeric value defining inner radius of annulus (in projection units)

- r2
Numeric value defining outer radius of annulus (in projection units)

- n
Number of samples

- ...
Additional arguments passed to spsample

##### Value

sp SpatialPointsataFrame OBJECT

##### Note

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

##### Examples

```
# NOT RUN {
library(sp)
library(rgeos)
data(meuse)
coordinates(meuse) <- ~x+y
proj4string(meuse) <- CRS("+init=epsg:28992")
xy <- meuse[2,]
rs100 <- sample.annulus(xy, r1=50, r2=100, n = 50, type = "random")
rs200 <- sample.annulus(xy, r1=100, r2=200, n = 50, type = "random")
plot(rs200, pch=20, col="red")
points(rs100, pch=20, col="blue")
points(xy, pch=20, cex=2, col="black")
box()
legend("topright", legend=c("50-100m", "100-200m", "source"),
pch=c(20,20,20), col=c("blue","red","black"))
# }
```

*Documentation reproduced from package spatialEco, version 1.3-2, License: GPL-3*

### Community examples

Looks like there are no examples yet.