rpoint

Generate N Random Points

Generate a random point pattern containing $n$ independent, identically distributed random points with any specified distribution.

Usage

rpoint(n, f, fmax=NULL, win=unit.square(), ..., giveup=1000, verbose=FALSE)

Details

This function generates n independent, identically distributed random points with common probability density proportional to f.

The argument f may be [object Object],[object Object],[object Object] The algorithm is as follows:

• Iffis a constant, we invokerunifpoint.
• Iffis a function, then we use the rejection method. Proposal points are generated from the uniform distribution. A proposal point$(x,y)$is accepted with probabilityf(x,y,...)/fmaxand otherwise rejected. The algorithm continues untilnpoints have been accepted. It gives up aftergiveup * nproposals if there are still fewer thannpoints.
• Iffis a pixel image, then a random sequence of pixels is selected (usingsample) with probabilities proportional to the pixel values off. Then for each pixel in the sequence we generate a uniformly distributed random point in that pixel.

See Also

ppp.object, owin.object, runifpoint

Aliases

• rpoint

Examples

# 100 uniform random points in the unit square
 X <- rpoint(100)

 # 100 random points with probability density proportional to x^2 + y^2
 X <- rpoint(100, function(x,y) { x^2 + y^2}, 1)

 # `fmax' may be omitted
 X <- rpoint(100, function(x,y) { x^2 + y^2})

 # irregular window
 data(letterR)
 X <- rpoint(100, function(x,y) { x^2 + y^2}, win=letterR)

 # make a pixel image 
 Z <- setcov(letterR)
 # 100 points with density proportional to pixel values
 X <- rpoint(100, Z)