| output.control {geoR} | R Documentation |
Auxiliary function defining output options for
krige.bayes and krige.conv.
output.control(n.posterior, n.predictive, moments, n.back.moments,
simulations.predictive, mean.var, quantile,
threshold, sim.means, sim.vars, signal, messages)
n.posterior |
number of samples to be taken from the posterior distribution. Defaults to 1000. |
n.predictive |
number of samples to be taken from the
predictive distribution. Default equals to
n.posterior. |
moments |
logical. Indicates whether the moments of the
predictive distribution are returned. If lambda = 1
there is no transformation/back-transformation.
If lambda = 0 or lambda = 0.5 the moments are
back-transformed by analytical expressions. For other cases the
back-transformation is done by simulation. Defaults to TRUE. |
n.back.moments |
number of sample to back-transform moments by simulation. Defaults to 1000. |
simulations.predictive |
logical. Defines whether to draw simulations
from the predictive distribution.
Only considered if prediction
locations are provided in the argument locations of the main functions.
Defaults to FALSE but changed to
TRUE if an integer greater then zero is provided in the
argument n.predictive and/or simulations are required in
order to compute quantities required by other arguments such as
threshold, quantiles and some values of the transformation parameter.
|
mean.var |
logical (optional). Indicates whether mean and variances of the simulations of the predictive distributions are computed and returned. |
quantile |
a (optional) numeric vector.
If provided indicates whether quantiles of the
simulations from the
predictive distribution are computed and returned.
If a vector with numbers in the interval
[0,1] is provided, the output includes the object
quantiles, which contains values of corresponding
estimated quantiles. For
example, if quantile = c(0.25, 0.50, 0.75) the function
returns the quartiles of the distributions at each of the
prediction locations.
If quantile = TRUE default values equals to c(0.025, 0.5,
0.975), are assumed.
A measure of uncertainty of the predictions, analogous to the kriging
standard error, can be computed by (quantile0.975 - quantile0.025)/4.
Only used if prediction locations are provided in the argument
locations. |
threshold |
a (optional) numerical vector.
If one or more values are provided, object named
probabilities is included in the output.
This object contains, for each
prediction location, the probability that the variable is less
than or equal than the threshold provided by the user.
Defaults to FALSE. |
sim.means |
logical (optional). Indicates whether mean
of each of the conditional simulations of the predictive
distribution should be computed and returned. Defaults to
TRUE if simulations from the predictive are required. |
sim.vars |
logical (optional). Indicates whether variance
of each of the conditional simulations of the predictive
distribution should be computed and returned. Defaults to FALSE. |
signal |
logical indicating whether the signal or the variable is
to be predicted. Defaults to NULL and changed internally in
the functions which call output.control. See DETAILS
below. |
messages |
logical. Indicates
whether or not status messages are printed on the output device
while the function is running. Defaults to TRUE. |
SIGNAL
This function is typically called by the geoR's prediction functions
krige.bayes and krige.conv
defining the output to be returned by these functions.
The underlying model
Y(x) = mu + S(x) + e
assumes that observations Y(x) are noisy versions of a signal S(x) and Var(e)=tau^2 is the nugget variance.
If tau^2 = 0 the Y and S are
indistiguishable.
If tau^2 > 0 and regarded as measurement error the
option signal defines whether the S (signal =
TRUE) or the variable Y (signal = FALSE) is to be
predicted.
For the latter the predictions will "honor" the data,
i.e. at data locations predictions will coincide with the data.
For unsampled locations, when there is no transformation of the data,
the predicted values will be the same
regardless whether signal = TRUE or FALSE but the
predictions variances will differ.
By default krige.bayes sets signal = TRUE
and krige.conv sets signal = FALSE.
The function krige.conv has an argument
micro.scale. If micro.scale > 0 the error term is
divided as e = e_{ms} +
e_{me} and the nugget variance is divided into two terms: micro-scale variance
and measurement error.
If signal = TRUE the term e_{ms} is
regarded as part of the signal and consequently the micro-scale variance is added to
the prediction variance.
If signal = FALSE the total error variance tau^2
is added to the prediction variance.
A list with processed arguments to be passed to the main function.
Paulo J. Ribeiro Jr. paulojus@leg.ufpr.br,
Peter J. Diggle p.diggle@lancaster.ac.uk.
The prediction functions krige.bayes and krige.conv.