| powerexp.gc {gcKrig} | R Documentation |
The Powered Exponential Correlation Function of Class corr.gc
Description
The powered exponential correlation function in spatial statistics.
By default, range parameter is not available, so
this function is used for likelihood inference and spatial prediction in function mlegc
and predgc.
Users need to specify the shape parameter kappa and if the correlation model includes a nugget effect
nugget = TRUE or not nugget = FALSE.
When both range and nugget parameters are given,
the function is used for simulation with function simgc in package gcKrig.
Usage
powerexp.gc(range = NULL, kappa = 1, nugget = TRUE)
Arguments
range |
a non-negative scalar of the range parameter in powered exponential correlation function. |
kappa |
a scalar between 0 and 2; the value of the shape parameter in the powered exponential correlation function. |
nugget |
the nugget effect of the correlation function. If specified, it must be a scalar between 0 and 1. |
Details
The powered exponential correlation function with a nugget \tau^2 is of the form:
\rho(h) = (1-\tau^2) exp((-h/\phi)^\kappa)
when h > 0 and \rho(h) = 1 when h = 0.
Here h is distance, \phi is range parameter, \kappa is the shape parameter and
\tau^2 is the nugget effect.
When using the powered exponential correlation function, note that 0<\kappa \le 2.
Value
An object of class corr.gc representing the correlation component.
Author(s)
Zifei Han hanzifei1@gmail.com