Dagum Covariance Model Family
RMdagum is a stationary isotropic covariance model.
The corresponding covariance function only depends on the distance r ≥ 0 between
two points and is given by
C(r) = 1-(1+r^(-β))^(-γ / β).
The parameters β and γ can be varied in the intervals (0,1] and (0,1), respectively.
RMdagum(beta, gamma, var, scale, Aniso, proj)
beta |
numeric in (0,1] |
gamma |
numeric in (0,1) |
var,scale,Aniso,proj |
optional arguments; same meaning for any
|
Like the generalized Cauchy model the Dagum family can be used to model fractal dimension and Hurst effect. For a comparison of these see Berg, C. and Mateau, J. and Porcu, E. (2008). This paper also establishes valid parameter choices for the Dagum family, but be careful because therein the model is parameterized differently.
Martin Schlather, schlather@math.uni-mannheim.de, https://www.wim.uni-mannheim.de/schlather/
Berg, C. and Mateau, J. and Porcu, E. (2008) The dagum family of isotropic correlation functions. Bernoulli 14(4), 1134–1149.
RFoptions(seed=0) ## *ANY* simulation will have the random seed 0; set ## RFoptions(seed=NA) to make them all random again model <- RMdagum(beta=0.5, gamma=0.5, scale=0.2) x <- seq(0, 10, 0.02) plot(model) plot(RFsimulate(model, x=x))
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