Brown-Resnick process
RPbrownresnick
defines a Brown-Resnick process.
RPbrownresnick(phi, tcf, xi, mu, s)
phi |
specifies the covariance model or variogram, see RMmodel and RMmodelsAdvanced. |
tcf |
the extremal correlation function; either |
xi, mu, s |
the extreme value index, the location parameter and the scale parameter, respectively, of the generalized extreme value distribution. See Details. |
The argument xi
is always a number, i.e. ξ is constant in space. In contrast, μ and s might be constant numerical values or (in future!) be given by an RMmodel
, in particular by an RMtrend
model.
For xi=0, the default values of mu and s are 0 and 1, respectively. For xi\not=0, the default values of mu and s are 1 and |ξ|, respectively, so that it defaults to the standard Frechet case if ξ > 0.
The functions RPbrorig
, RPbrshifted
and RPbrmixed
perform the simulation of a Brown-Resnick process, which is defined by
Z(x) = max_{i=1, 2, ...} X_i * exp(W_i(x) - gamma^2),
where the X_i are the points of a Poisson point process on the
positive real half-axis with intensity 1/x^2 dx,
W_i ~ Y are iid centered Gaussian processes with
stationary increments and variogram gamma given by
phi
.
For simulation, internally, one of the methods
RPbrorig
, RPbrshifted
and
RPbrmixed
is chosen automatically.
Advanced options
are maxpoints
and max_gauss
, see
RFoptions
.
Further advanced options related to the
simulation methods RPbrorig
,
RPbrshifted
and RPbrmixed
can be
found in the paragraph ‘Specific method options for Brown-Resnick
Fields’ in RFoptions
.
Brown, B.M. and Resnick, S.I. (1977). Extreme values of independent stochastic processes. J. Appl. Probab. 14, 732-739.
Buishand, T., de Haan , L. and Zhou, C. (2008). On spatial extremes: With application to a rainfall problem. Ann. Appl. Stat. 2, 624-642.
Kabluchko, Z., Schlather, M. and de Haan, L (2009) Stationary max-stable random fields associated to negative definite functions Ann. Probab. 37, 2042-2065.
Oesting, M., Kabluchko, Z. and Schlather M. (2012) Simulation of Brown-Resnick Processes, Extremes, 15, 89-107.
RFoptions(seed=0) ## *ANY* simulation will have the random seed 0; set ## RFoptions(seed=NA) to make them all random again ## for some more sophisticated models see 'maxstableAdvanced'
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