Learn R Programming

geoR (version 1.0-8)

xvalid: Cross-validation using kriging

Description

This is a function to perform model validation. Options include leaving-one-out cross-validation where. each data location is removed from the data set and the variable at this location is predicted using the remaining locations, for as given model. This can be done for all or some of the locations. Alternativelly, other validation locations which are not the same as the original data locations can be used.

Usage

xvalid(geodata, coords = geodata$coords, data = geodata$data,
       model, reestimate = FALSE, variog.obj = NULL,
       output.reestimate = FALSE, locations.xvalid = "all",
       data.xvalid = NULL, messages.screen = TRUE, ...)

Arguments

geodata
a list containing element coords as described next. Typically an object of the class "geodata" - a geoR data-set. If not provided the arguments coords must be provided instead.
coords
an $n \times 2$ matrix containing coordinates of the $n$ data locations in each row. Defaults to geodata$coords, if provided.
data
a vector or matrix with data values. If a matrix is provided, each column is regarded as one variable or realization. Defaults to geodata$data, if provided.
model
an object containing information on a fitted model. Typically an output of likfit, variofit.
reestimate
logical. Indicates whether or not the model parameters should be re-estimated for each point removed from the data-set.
variog.obj
on object with the empirical variogram, typically an output of the function variog. Only used if reestimate = TRUE and the object passed to the argument model is the re
output.reestimate
logical. Only valid if reestimate = TRUE. Specifies whether the re-estimated parameters are returned.
locations.xvalid
there are three possible specifications for this argument: "all" indicates the leaving-on-out method is used. The second possibility is to use only a sub-set of the data for cross-validation. For this case a vector shoul
data.xvalid
data values at the validation locations. Only used if the validation locations are not the same or a subset of the original data coordinates.
messages.screen
logical. Indicates whether status messages should be printed on the screen (or output device) while the function is running.
...
further arguments to the minimization functions used by likfit, variofit.