Quantile Tessellation
Divide space into tiles which contain equal amounts of stuff.
quantess(M, Z, n, ...) ## S3 method for class 'owin' quantess(M, Z, n, ..., type=2, origin=c(0,0), eps=NULL) ## S3 method for class 'ppp' quantess(M, Z, n, ..., type=2, origin=c(0,0), eps=NULL) ## S3 method for class 'im' quantess(M, Z, n, ..., type=2, origin=c(0,0))
M |
A spatial object (such as a window, point pattern or pixel image) determining the weight or amount of stuff at each location. |
Z |
A spatial covariate (a pixel image or a |
n |
Number of bands. A positive integer. |
type |
Integer specifying the rule for calculating quantiles.
Passed to |
... |
Additional arguments passed to |
origin |
Location of the origin of polar coordinates,
if |
eps |
Optional. The size of pixels in the approximation which is used to compute the quantiles. A positive numeric value, or vector of two positive numeric values. |
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.
The result of quantess is a tessellation of as.owin(M)
determined by the quantiles of Z.
A tessellation (object of class "tess").
Original idea by Ute Hahn.
Implemented in spatstat by
Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.
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)
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