spatstat.geom (version 3.6-0)

quantess: Quantile Tessellation

Description

Divide space into tiles which contain equal amounts of stuff.

Usage

quantess(M, Z, n, ...)
# S3 method for owin
quantess(M, Z, n, ..., type=2, origin=c(0,0), eps=NULL)
# S3 method for ppp
quantess(M, Z, n, ..., type=2, origin=c(0,0), eps=NULL)
# S3 method for im
quantess(M, Z, n, ..., type=2, origin=c(0,0))

Value

A tessellation (object of class "tess").

Details

A quantile tessellation is a division of space into pieces which contain equal amounts of stuff.

The function quantess computes a quantile tessellation and returns the tessellation itself. The function quantess is generic, with methods for windows (class "owin"), point patterns ("ppp") and pixel images ("im").

The first argument M (for mass) specifies the spatial distribution of stuff that is to be divided. If M is a window, the area of the window is to be divided into n equal pieces. If M is a point pattern, the number of points in the pattern is to be divided into n equal parts, as far as possible. If M is a pixel image, the pixel values are interpreted as weights, and the total weight is to be divided into n equal parts.

The second argument Z is a spatial covariate. The range of values of Z will be divided into n bands, each containing the same total weight. That is, we determine the quantiles of Z with weights given by M.

For convenience, additional arguments ... can be given, to further subdivide the tiles of the tessellation. These arguments should be recognised by one of the functions quadrats or tess. The tessellation determined by these arguments is intersected with the quantile tessellation.

The result of quantess is a tessellation of as.owin(M) determined by the quantiles of Z.

See Also

tess, quadrats, quantile, tilenames

Examples

  plot(quantess(letterR, "x", 5))

  plot(quantess(bronzefilter, "x", 6))
  points(unmark(bronzefilter))

  plot(quantess(letterR, "rad", 7, origin=c(2.8, 1.5)))
  plot(quantess(letterR, "ang", 7, origin=c(2.8, 1.5)))

  opa <- par(mar=c(0,0,2,5))
  A <- quantess(Window(bei), bei.extra$elev, 4)
  plot(A, ribargs=list(las=1))
  
  B <- quantess(bei, bei.extra$elev, 4)
  tilenames(B) <- paste(spatstat.utils::ordinal(1:4), "quartile")
  plot(B, ribargs=list(las=1))
  points(bei, pch=".", cex=2, col="white")
  par(opa)