gblemp | R Documentation |
Calculates empirical gliding box lacunarity of a binary map, which was proposed by Allain and Cloitre (1991).
gblemp(boxwidths, xiim, obswin = Frame(xiim)) gbltrad(boxwidths, xiim, obswin = Frame(xiim))
boxwidths |
A list of suggested box widths in the same units as |
xiim |
An image of pixels valued either |
obswin |
Optional observation window. The observation window used for the estimator will be the intersection of |
Calculates empirical gliding box lacunarity (Allain and Cloitre, 1991) for a given range of square box sizes,
1 + Var(area(B . xi)) / E[area(B . xi)]^2,
where B is a box that has a random location in the observation window and area(B . xi) is the (random) area of the foreground in B. This is an estimate of the gliding box lacunarity of a RACS (Hingee et al., 2017).
The algorithm uses the pixel locations in xiim
as an array of box centre locations to compute
the mean and variance of the area in a random box of a given size.
Locations where the box is not completely within the observation window are ignored.
An fv
object containing empirical GBL, variance of the area in the box and mean of the area in the box.
The box widths (labelled s
) are always odd multiples of the pixel width.
gbltrad
: An alias of gblemp
used in past versions of this package. This alias may be removed in future versions.
The box side lengths are rounded such that they are an odd number of pixels across.
gblemp
uses the roll_sum
function in RcppRoll to operate, so RcppRoll must be installed to run gblemp
.
Allain, C. and Cloitre, M. (1991) Characterizing the lacunarity of random and deterministic fractal sets. Physical Review A, 44, 3552-3558.
Hingee K, Baddeley A, Caccetta P, Nair G (2019). Computation of lacunarity from covariance of spatial binary maps. Journal of Agricultural, Biological and Environmental Statistics, 24, 264-288. DOI: 10.1007/s13253-019-00351-9.
xiim <- as.im(heather$coarse, na.replace = 0) boxwidths <- seq(0.2, 14, by = 0.2) #in units of xiim gblest <- gblemp(boxwidths, xiim)
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