spatstat (version 1.23-1)

rthin: Random Thinning

Description

Applies independent random thinning to a point pattern.

Usage

rthin(X, P, ...)

Arguments

X

A point pattern (object of class "ppp") that will be thinned.

P

Data giving the retention probabilities, i.e. the probability that each point in X will be retained. Either a single number, or a vector of numbers, or a function(x,y), or a pixel image (object of class "im"

...

Additional arguments passed to P, if it is a function.

Value

• A point pattern (object of class "ppp").

Details

In a random thinning operation, each point of the pattern X is randomly either deleted or retained (i.e. not deleted). The result is a point pattern, consisting of those points of X that were retained.

Independent random thinning means that the retention/deletion of each point is independent of other points.

The argument P determines the probability of retaining each point. It may be [object Object],[object Object],[object Object],[object Object] If P is a function, it should be vectorised, that is, it should accept vector arguments x,y and should yield a numeric vector of the same length. The function may have extra arguments which are passed through the ... argument.

Examples

data(redwood)
  plot(redwood, main="thinning")
  
  # delete 20\% of points
  Y <- rthin(redwood, 0.8)
  points(Y, col="green", cex=1.4)

  # function
  f <- function(x,y) { ifelse(x < 0.4, 1, 0.5) }
  Y <- rthin(redwood, f)

  # pixel image
  Z <- as.im(f, redwood$window)
  Y <- rthin(redwood, Z)